Officials and analysts in the United States have been warning that al-Qaida or associated groups are planning such attacks on American soil.
Dubbed American Hiroshima, the plan apparently targets New York, Miami, Los Angeles, Philadelphia, Chicago, San Francisco, Las Vegas, Boston and Washington, DC.
Former US Defence Secretary William Perry says there is an even chance of a nuclear attack on the US this decade. Renowned investor Warren Buffet has predicted "a nuclear terrorist attack ... is inevitable".
David Dionisi, a former US army intelligence officer, is convinced that plans for a nuclear attack are under way.
Once a conservative Republican, Dionisi enjoyed success as a Fortune 500 business executive after leaving the army. But he later rejected his political beliefs and now advocates peace, social justice and humanitarianism.
In his new book, American Hiroshima, Dionisi argues decades of unjust US foreign policies will be largely to blame for sowing the seeds of hostility and vengeance which could lead to a nuclear catastrophe.
Aljazeera's Shaheen Chughtai caught up with Dionisi in London.
Dionisi had just flown from Liberia where he helps run a Catholic orphanage.
Aljazeera.net: You were once a conservative Republican. What made you change your beliefs?
Dionisi: The transformation was a discovery process. When I joined the military, I had a very limited view of what the US was doing around the world. Through my experiences as a military intelligence officer and later as a business executive doing international volunteer work, I started to see our foreign policies were often hurting people and making the world more dangerous.
One of the more dramatic moments in this process was when I was assigned to a unit focusing on implementing US foreign policy in central America. I was part of a rapid deployment team designed to go in and suppress forces working for social justice in places such as Honduras, Nicaragua, El Salvador and Guatemala.
You describe the US public as uninformed - why?
The major media outlets are owned by a handful of corporations interested in promoting advertising and pro-government messages. Anything that challenges the existing power structure very often fails to receive air time. I highlight Fox as an extreme example of the Republican propaganda machine.
But when your country is fighting a war, you have an obligation to understand what's really going on. If you don't, you can become an agent of injustice. If people can find the time to watch baseball or soccer etc, they can make an effort to read, travel, talk and not be limited to the messages of fear.
They also need to understand their history. In 1962, the Joint Chiefs of Staff presented a plan called Operation Northwood, which is now declassified. It proposed conducting mass casualty attacks on American targets and blaming it on Cuba to rally public support for war against Fidel Castro. President Kennedy rejected the plan. So we shouldn't just assume any future attack on our soil is the work of al-Qaida.
Your book condemns alliances with repressive regimes. Can't these be justified if they serve a greater cause?
History teaches us that when you form alliances that promote injustice, you can only expect injustice in the future. Kindness begets kindness and the inverse is also true.
The US fought the largest secret war in its history during the 1980s in Afghanistan - over $6bn was funnelled into that war. As a result, US collaboration with and responsibility for al-Qaida goes well beyond what most even informed Americans understand.
If you consider that there are over 500 prisoners in Guantanamo Bay from over 40 countries - though not a single one is from Iraq - and that the CIA recruited thousands of people from over 40 countries to be part of that war - none from Iraq - you can better understand how the US played a direct role in creating what became the Taliban and al-Qaida.
Bush supporters argue the removal of Saddam and the Taliban was beneficial and therefore justified military action.
That starts from an artificial premise. When the Bush administration says, "Well, it's great that Saddam's gone," it fails to acknowledge that Bush's father and President Ronald Reagan were key forces that helped create Saddam Hussein.
Looking at what happened in 1979 it can put a lot of this in perspective. As Reagan came into office, the US embassy hostages in Iran were released after 444 days in captivity. Americans don't know this wasn't a coincidence. The US had agreed in writing not to attack Iran and also paid Tehran $8bn. That's why that media event (of the hostages' release during Reagan's inauguration ceremony) occurred with such precise timing.
How do you know this?
These are facts that were subsequently published. The agreement with Iran was submitted for review by the current administration to see if it would be binding and prevent an attack in the near future.
Bush administration attorneys concluded it was signed under duress and therefore not binding. I know this from a former senior member of the Bush administration, a seasoned CIA officer named Ray Flynn.
The US felt humiliated; the Reagan administration wanted to hurt the Iranians but its hands were tied. So Saddam Hussein was used as the agent for that. He ended up invading Iran ... and you had this brutal war from 1980 to 1988 that killed over a million people.
What was the US role in that war?
By 1982, Iran had recaptured lost territory and Saddam asked the US for help. So President Reagan signed a National Security Decision Directive - NSDD 114 - to provide all means of support to Saddam Hussein. Donald Rumsfeld then went on a very sensitive mission to deliver satellite intelligence, other forms of intelligence and weapons of mass destruction (WMD).
That's why the current Bush administration was so confident Saddam had chemical and biological weapons; they knew the US had supplied the ingredients in the 1980s.
Saddam broke with the US, however, when he found out we were selling weapons to Iran in the mid-1980s - the Iran-Contra affair. All this puts the invasion of Kuwait into perspective. Saddam got clear messages from the US saying he could invade; plus he felt the US owed him one after betraying him over Iran.
All these wars form a continuum of injustice. Look at the UN economic sanctions in the 1990s that the US and UK refused to lift: over a million Iraqis died, including 500,000 children. That's more than the number who died from the Nagasaki and Hiroshima atomic bombings.
You list numerous "unjust" actions that led to attacks on US targets - isn't that justifying terrorism?
I talked to the CIA's Michael Scheuer, head of the "find Bin Ladin" team, and he stresses that people in the Muslim world are not fighting us because of our freedoms or elections but our foreign policy. This is something the Bush administration constantly twists.
The basic principle is: if you hurt someone, they're going to want to hurt you. We need to ask questions like: Why did 9/11 happen? Bin Ladin has a very clear articulation of why he's at war with the US, Britain, Israel and others. If Americans read it, they'll see it's very clear about things such as US forces on Arab land.
And it's not just an Arab or Muslim issue. I learnt this in South Korea where the US has had troops since 1950. When you're there that long, it sends a powerful message that you're not there to liberate, you're there to occupy.
You describe the US as the biggest WMD proliferator. Why?
The US has spent $5 trillion on 70,000 nuclear weapons since 1945 - more than the rest of the world combined. A Congressional report in 1999 found the designs for every deployed nuclear warhead - and for some not built yet - had been stolen and passed to China. Israel acquired its programme from the US too.
Despite this, ordinary Americans are more concerned about the Bush administration's lies and hyped-up warnings about WMD in places such as Iraq.
Is Iran really a threat to the US? An alliance between Shia Iran and Sunni-led al-Qaida seems far fetched.
Iran will not attack the US if the US does not attack Iran. Congressman Curt Weldon (who accuses Tehran of plotting to attack the States) talks about attacking Iran but such talk makes the world more dangerous. If we were Iran, we'd develop nuclear weapons simply because Israel has them. So the US should facilitate a process whereby Israel eliminates its nuclear weapons.
As for the religious differences between Iran and al-Qaida, yes, that's been true - but Bush's War on Terror has been pushing the sects together. Intelligence reports indicate Bin Ladin's son Saad has been based in Iran. No, we can't be certain they're helping each other. But in any case, the Bush administration does not want peace with Iran.
You say "kindness begets kindness". What's your evidence?
After the first world war, the Treaty of Versailles punished Germany harshly, producing hardship and hostility that the Nazis exploited. But after the second world war, when the Marshall Plan helped rebuild Germany and Japan, the US did more to promote democracy than at any time during the Cold war.
To make the world a safer place, we must aggressively attack the causes of suffering and hostility. Imagine if Bush had said after 9/11: "People are capitalising on our mistakes in the Middle East. So, let's ensure there is no hunger, lack of clean water, lack of education etc in the Muslim world." We would have made more friends and drained support for our enemies.
If we can't expect US foreign policy to change soon, isn't it too late to stop an American Hiroshima?
It's not too late although your point is realistic. But we can still influence the US response. Far more people will die in the retaliation and the counter-retaliation.
If the US had the wisdom, we could make the world safer. The US military budget was over $420 billion in 2005. We could split that three ways: a third on economic development in the Middle East, especially Iraq; a third on tackling injustice at home, such as providing universal healthcare - and that would still leave us with the world's biggest military budget.
People have to become more involved. The anti-Vietnam war movement is an example - but it failed to hold government to account. If we had tried (former Defence Secretary) Robert McNamara or (former Secretary of State) Henry Kissinger for crimes such as the illegal bombing of Cambodia, it would have sent a powerful message to future leaders. The Bush government today wouldn't have been so bold.
Ultimately, Americans need to understand many of them will die and parts of their country will become uninhabitable unless they hold their government to account.