In a relatively surprising development, Iran signed an agreement with Turkey and Brazil in Tehran on Monday by which it will ship most of its low enriched uranium to Turkey in exchange for the 20-percent uranium fuel needed for its Tehran reactor.

In response, the White House said Monday that the United States continues to have serious concerns over Iran.

White House spokesman Robert Gibbs said later in a regular briefing that the deal "does not change the steps that we are taking to hold Iran responsible for its obligations, including sanctions."

Nonetheless, analysts and media here said the deal might weaken the U.S. push for sanctions on Iran in the UN Security Council.

"Brazil and Turkey have argued that because of this deal, sanctions are unnecessary. We have to see in the next few days if Russia and China change their positions on sanctions," James Acton, an expert on the Iranian nuclear issue at the Carnegie Endowment for International Peace, told Xinhua.

"If Iran does notify the IAEA in seven days that it intends to proceed with the fuel swap, and it negotiates in good faith to implement the fuel swap, if after that it cooperates more seriously with the IAEA in terms of the questions on its nuclear program, then the deal could end up being a very good thing to help solve the problem," he said.

The New York Times also said the agreement could weaken the Obama administration's chances of securing international approval for punitive measures against Iran.

However, like many experts here, Acton believed that Iran's move is largely a tactical measure to avoid sanctions.

"I think U.S. will try very hard to continue with sanctions. It will argue the only reason Iran sat down with Turkey and Brazil is because of the threat of the sanctions. What is unclear now is whether U.S. is going to succeed," Acton said.

The United States and its Western allies have been long accusing Iran of trying to develop nuclear weapons, a charge always denied by Iran. The United States has recently stepped up its efforts to push for a fourth round of UN sanctions on Iran since December 2006.

According to a draft proposal, Iran agreed that it will send some 1,200 kg of its 3.5 percent enriched uranium over to Turkey in exchange for a total of 120 kg 20 percent uranium needed for a medical research reactor.

The deal resembles the one proposed by the United States, France and Russia about eight months ago. Iran had rejected the deal at the time, insisting on a simultaneous swap of the fuel on its soil.

The Washington Post said on its website that Iran appears to have scored a victory on Monday in the long-running diplomatic battle between Iran and the West, because Iran has seemingly made progress without offering any real compromise.

Ironically, the Obama administration now faces the uncomfortable prospect of rejecting a proposal it offered in the first place -- or seeing months of effort to enact new sanctions derailed, the newspaper said.