"We will take any necessary action so that Iran is aware of the choice it has to make to start to play its part as a full and respected member of the international community or face further isolation," Brown said on Monday.
Bush warned that he had not ruled out the use of force to end Iran's nuclear work, but said that he hoped to end the crisis diplomatically.
"Now's the time to work together to get it done," Bush said. "All options are on the table, however."
|The British and American leaders stood |
shoulder-to-shoulder on foreign policy [AFP]
The EU has not yet announced the stronger sanctions, but a spokeswoman for Javier Solana, the EU foreign affairs and security chief who failed last weekend to win Iran's support for a package of incentives, said EU foreign ministers meeting in Luxembourg on Monday were prepared to take formal action.
"It is clear they are ready to move further. We will definitely take a formal decision," Cristina Gallach said.
An EU diplomat said Tehran's refusal to accept the package Solana presented left the bloc with no choice but firm action in the run-up to an EU leaders' summit this week in Brussels.
More than 80 per cent of Iran's revenues come from oil exports and sanctions targeting its oil and gas industries could severely affect its already fragile economy.
High inflation and rampant unemployment have damaged its economy.
The sanctions could also have an impact on the already soaring global oil prices.
More British troops
Brown also said at the joint news conference with Bush that Britain would send more troops to Afghanistan.
"Today, Britain will announce additional troops for Afghanistan, bringing our numbers in Afghanistan to the highest level," Brown said.
The announcement came as the body of the 100th British troop to die in Afghanistan since operations began in 2001 was being sent home.
Brown also announced that Britain would
send more troops to Afghanistan [EPA]
The move is expected to take the number of British soldiers to about 8,000 in the country where they have been involved in fierce fighting with the Taliban.
"We have resolved ... it is in the British national interest to confront the Taliban in Afghanistan, or Afghanistan would come to us," Brown said at the conference.
"Eighteen months ago, the Taliban boasted that they and their paid foreign fighters would drive our forces out of southern Helmand.
"Now, most agree that security is on the way to being transformed."
His announcement came as the Taliban took control of 10 villages about 30km north of Kandahar city and triggered a scramble by Afghan and Nato forces to defend the southern Afghanistan city.
Britain has approximately 7,800 soldiers in Afghanistan, most of whom are in Helmand fighting the Taliban, who have been fighting since being removed from power in the 2001 US-led invasion of the country.