Barack Obama has expressed hope that a new regime of sanctions against Iran would be ready for passage at the UN "within weeks".
Standing at his side, the President of France, Nicolas Sarkozy, reaffirmed that Tehran must end its "mad race" towards acquiring nuclear weapons.
The remarks came at a joint press conference in the White House after a brief summit between the country's leaders. Their talks were to be followed by a rare private dinner for both heads of state in the White House with the first ladies of both countries – Michelle Obama and Carla Bruni – also at the table.
A US spokesman earlier pushed back on speculation that Mr Obama would use the occasion to ask France to send more troops to Afghanistan. But Mr Sarkozy spoke supportively of the US strategy on the ground, adding that "we cannot afford to lose" the war. "By fighting in Afghanistan, what we are fighting for is world security, quite simply," the French President said.
On Iran, Mr Sarkozy said that the, "time has come to make decisions". Mr Obama added: "On this the United States and France are united." Making it clear that his patience on the issue is now running out, he went on: "My hope is that we are going to get this done this spring."
Mr Obama acknowledged that unanimity between nations on passing new sanctions on Iran has not yet been achieved. Recent weeks have seen an apparent willingness on the part of Russia to support a new regime while China has continued to signal some resistance. But he said, "We think we can get sanctions within weeks".
Both men were eager to use the joint appearance to lessen any impression of tensions between the two of them. While in a speech in New York on Monday Mr Sarkozy had cautioned the US against trying to "run the world alone". In the company of Mr Obama he was at pains to complement him on everything from the passage of US healthcare reform to his position condemning new settlements in Israel.
When Mr Obama "says something, he keeps his word," Mr Sarkozy said. "His word is his bond and that is so important. When he can he delivers, when he can't he says so." On the settlements dispute, Mr Sarkozy said that, "the settlement process contributes nothing and does nothing for Israel's security".
Mr Obama was meeting with Mr Sarkozy a day after returning from his surprise visit to Afghanistan. He said earlier yesterday that he had found Hamid Karzai, the country's President, a man who acknowledges "the incredible opportunity he has to be the father of modern Afghanistan".
The meeting was said to have been tense, however, as Mr Karzai continues to attract criticism for failing to crack down on corruption and cronyism in his government. "I think he is listening but I think that the progress is too slow, and what we've been trying to emphasise is the fierce urgency of now," Mr Obama told NBC News. "On all those issues we've got to make progress faster and we can't dilly-dally around."
Yesterday, Canada made clear that it would withdraw all of its military personnel from Afghanistan by the end of next year. Attending a G8 meeting of foreign ministers in Ottawa, the US Secretary of State, Hillary Clinton, hinted on Monday that the US would like to see Canadian forces remain beyond 2011. But Canada's Prime Minister, Stephen Harper, yesterday told Mrs Clinton directly that his country's military involvement would end before the end of next year.