To critics in the Middle East and on Capitol Hill, anything short of a full agreement may be seen as merely allowing the Iranians to stall for time, potentially reaping billions of dollars in eased economic sanctions while still refining their nuclear technology. It could also make it harder for President Barack Obama to hold off a congressional push for tougher sanctions on Iran, which the White House has warned would upend the fragile diplomacy.
The United States and its five partners—Britain, France, Germany, Russia and China—plan to resume face-to-face negotiations with the Iranians next month. They secured a six-month agreement in November that went into effect just this Monday. That deal froze key parts of Iran's nuclear program in exchange for easing some trade and financial penalties. Though it included a provision to renew the short-term accord for a period of time that would have to be agreed to by all parties, it also aimed to clear the way for broader negotiations on the thorniest aspects of Iran's nuclear program.
But analysts say another short-term deal may be the only feasible outcome given the vast differences between Tehran and the international coalition.
"I think it's extremely unlikely that it will be possible to reach a comprehensive agreement in the next six months," said Gary Samore, who until last year was Obama's top arms control adviser. "We're in for a rolling series of extensions."
The talks could also crumble completely if Iran violates the terms of the agreement or the parties make no progress in moving the negotiations forward.
It's not clear what the U.S. and its coalition partners would do if a comprehensive agreement isn't reached in six months. U.S. officials are currently meeting with their counterparts in the so-called P5+1 to plot strategy for the February meetings.
French Foreign Ministry spokesman Romain Nadal told The Associated Press on Thursday that the coalition's priority is to reach a big deal and do so quickly.
"We are not going to go through a succession of interim deals," Nadal said. He added that the push in Congress for tougher sanctions against Iran "increases the pressure."
The White House has so far been able to hold off a Senate vote on a sanctions bill, arguing that it would violate the terms of the interim agreement with Iran and could disrupt diplomacy, even if Obama vetoes the bill. But congressional aides say even those who support Obama's outreach to Iran could buckle if forced to accept another six-month deal.
Backers of the congressional sanctions push say the crippling economic penalties are what's drawn Iran to the negotiating table in the first place and should not be eased until the Islamic republic bends on all international demands. Many have been unmoved by Obama's pleas to hold off on legislation.
"It's time to schedule a vote on the bill to give the American people the diplomatic insurance policy they deserve," says Sen. Mark Kirk, R-Ill., a leading sanctions advocate.
The prospect of Iran using interim agreements as a delaying tactic has also stoked concern in the Middle East, particularly in Israel, which sees an Iranian nuclear program as a threat to its very existence. Senior Israeli officials say they're concerned that even if Iran complies with the terms of interim agreements, the nature of those accords will allow the Islamic republic to keep key elements of its program intact.
Yet pushing directly for a comprehensive pact is not without pitfalls. Negotiations are likely to be far thornier than in the months of discussions that went into producing the interim agreement. And any final pact, U.S. officials have stressed, must settle once and for all any concerns that Iran may be trying to produce nuclear weapons.
Iran has denied it is seeking a bomb and says it is pursuing nuclear capabilities for peaceful purposes.
In a report released this week, David Albright, a former U.N. weapons inspector who regularly consults with the Obama administration, said Iran must remove some 15,000 of its estimated 20,000 centrifuges to make a final agreement palatable for the United States. Albright, whose report drew on discussions with senior U.S. officials, also said Tehran would have to shut down an underground uranium enrichment site and significantly downgrade its heavy water reactor.
Iran has never come close to accepting such conditions. They would eliminate the possibility of a plutonium-based weapon core, and extend by several months the timespan needed for Iran to "break out" through higher-grade uranium enrichment toward nuclear weapons development.
As of now, Iran insists it isn't required to "dismantle" any parts of its nuclear program. Speaking at the World Economic Forum in Davos, Switzerland, President Hassan Rouhani said his country would honor the interim deal and was ready to do business with the world.
Associated Press writer Jamey Keaten in Paris contributed to this report.