Iran nuclear talks continue as deadline looms in Switzerland

LAUSANNE, Switzerland — Will they or won't they? Iran and six world powers buckled down on Tuesday in a last-ditch attempt to hammer out a nuclear deal with less than 24 hours to go before a self-imposed deadline.

Diplomats from Iran and the so-called P5+1 — the U.S. China, Russia, Germany, France and Britain — are scrambling to agree on the framework of an agreement that would see Iran limit its nuclear program in exchange for some sanctions relief.

Talks over the past week in Switzerland intensified as the midnight Tuesday deadline (6 p.m. ET) approached, with all sides swinging between cautious optimism and warning that differences remained which could derail a long-awaited deal to end a decade-long nuclear standoff.

Officials said negotiators Tuesday were working on pulling together a statement that would close the round of talks but leave several key issues to be decided in the coming months — while carefully avoiding mention of an "extension."

While all signs point to the issuance of a statement today, U.S. officials warned there was still a possibility on failing to even agree to that.

One of the talks' biggest sticking points, according to U.S. negotiators, has been getting Iran to curtail its research and development on nuclear activity for at least 10 years but potentially longer. Another has been on the timing of sanctions relief for Iran if a deal is reached.

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Iran has been insisting on the removal of sanctions up front — though the U.S. and several of its allies have resisted, insisting they need some sort of leverage to ensure Tehran sticks to the deal.

Failure to break through logjams on these key points would make it significantly harder for the Obama administration to fight off pending congressional legislation to assert control over any future deal — a move the White House has said will sabotage future negotiations to finalize the agreement with Iran.

It was not immediately clear what impact Tuesday's outcome would have on the comprehensive-deal's target of June 30. Iran and the six powers have twice extended their deadline for a long-term agreement after reaching an interim accord in November 2013.

"I can't rule out that there will be further crises in these negotiations," German Foreign Minister Frank-Walter Steinmeier said told reporters on Monday, noting that there had been "some progress and some setbacks in the last hours."

He and his French counterpart Laurent Fabius cancelled plans to depart for a meeting in Berlin to stay overnight as talks entered a critical phase.

As Kerry and his counterparts sat down Tuesday with Iran's Foreign Minister Jawad Zarif, a reporter asked if a deal could be reached that day. "You'll have your answer before the end of the day," Kerry replied, then smiled.

NBC News' Andy Eckardt contributed to this report.

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