"We have made our bottom line clear: For the safety of our people and the peace of the world, America will not allow Iran to develop a nuclear weapon," Bush told the Saban Forum, a Middle East policy forum sponsored by the Brookings Institution.
Bush defended his decision to invade Iraq in March 2003 and topple Saddam Hussein, the country's former leader, saying that after the September 11 attacks in 2001, the US could not risk the alleged threat Baghdad posed at that time.
"It is true, as I have said many times, that Saddam Hussein was not connected to the 9/11 attacks," Bush said.
But the US had to decide whether it could tolerate an enemy that allegedly supported terrorism and was believed to have weapons of mass destruction, and he said the US found "this was a risk we could not afford to take".
"When Saddam's regime fell, we refused to take the easy option and install a friendly strongman in his place," Bush said.
"Even though it required enormous sacrifice, we stood by the Iraqi people as they elected their own leaders and built a young democracy."
Bush, the first sitting US president to call for an independent Palestinian state, defended his approach to ending the six-decade conflict despite the lack of any concrete progress from US-backed negotiations.
"On the most vexing problem in the region - the Israeli-Palestinian conflict - there is now greater international consensus than at any point in recent memory," he said.
|Palestinians are likely to be sceptical about the
progress Bush has made [AFP]
Bush called the two-state approach "one of the highest priorities of my presidency," and described talks at a US-sponsored November 2007 conference in Annapolis, Maryland, as "determined and substantial".
"While the Israelis and Palestinians have not yet produced an agreement, they have made important progress," he said.
Hillary Mann, a former Bush administration foreign policy official, told Al Jazeera that her experience of working with the US leader on the Israeli-Palestinian conflict was different.
"When I worked for him, before we came up with the roadmap agreement of 2001-2003 ... he didn't think you needed a roadmap, he thought a speech was all you needed," he said.
"But reality doesn't work that way and that has been Bush's biggest enemy - reality."
Bush also cited Lebanon's Cedar Revolution against Syrian involvement in the county, Libya's decision to end its nuclear weapons programme, increased enthusiasm for democratic reforms, and prosperity in places such as the United Arab Emirates.
Jon Alterman, the director of the Middle East Programme at the Washington-based Centre for Strategic and International Studies, told Al Jazeera the speech lacked vision.
"It is true, as I have said many times, that Saddam Hussein was not connected to the 9/11 attacks."
"His presidency has lost energy and confidence and he is just looking step aside," he said.
"It felt almost like a medley or greatest hits, it didn't have the same energy or boldness, it was almost watered down.
"The president knows when peace happens, some other president will take the credit, no one will say Bush is the man that set it up, they sense that Bush set these things back."
Equally critical of Bush's comments was Abdullah Schleifer, a political analyst from the American University in Cairo. Speaking to Al Jazeera, he said: "It is as if he has reverted to type ... he talked about Syria and Iran in the same old context of 'you are not with us, you are against us'.
"There was no reference to negotiations. The whole role of diplomacy and negotiations is on the backburner as far as President Bush is concerned."