President Barack Obama rejected criticism from Republicans over foreign policy, particularly his handling of Iran's nuclear ambitions, according to an interview extract released Wednesday.

"I have made myself clear since I began running for the presidency that we will take every step available to prevent Iran from obtaining a nuclear weapon," Democrat Obama told Time Magazine.

"Can we guarantee that Iran takes the smarter path? No, which is why I've repeatedly said we don’t take any options off the table in preventing them from getting a nuclear weapon."

The US president said the Republicans seeking to replace him, including the frontrunner Mitt Romney, were attempting to win backing from the party faithful and secure the nomination by attacking his foreign policy decisions.

"I think Mr Romney and the rest of the Republican field are going to be playing to their base until the primary season is over," Obama said during a White House interview that will appear in Time's January 30 issue.

"Overall, I think it's going to be pretty hard to argue that we have not executed a strategy over the last three years that has put America in a stronger position than it was than when I came into office," he added.

The US president will bid for a second term in a November 6 election.

Romney said on January 1 that Obama had failed in his efforts to get Iran to abandon its suspect nuclear program.

"I want to make sure that the people of this nation understand that he failed us not only here at home, he's failed us in dealing with the greatest threat we face, which comes from Iran," Romney said.

The West alleges Tehran is seeking to acquire a weapons capability under the guise of its nuclear research program. Iran denies any such ambition and says its work is only for civil energy and medical purposes.

In the Time interview, Obama also contrasted his tenure with that of his predecessor, the Republican president George W. Bush, who led the United States into expensive wars in Afghanistan and Iraq.

"It's a US leadership that recognizes our limits in terms of resources and capacity," Obama said of his foreign policy decisions.

"And yet, what I think we've been able to establish is a clear belief among other nations that the United States continues to be the one indispensable nation in tackling major international problems."