LAUSANNE, Switzerland, April 1 (UPI) -- Negotiations over Iran's nuclear program are entering double overtime as yet another deadline passed Wednesday without an agreement in place, officials said.
The negotiations, taking place in Lausanne, Switzerland, are being held by the foreign ministers of the United States, the United Kingdom, France, Russia, China and Germany with Iranian Foreign Minister Mohammad Javad Zarif. A self-imposed deadline was initially set for Tuesday to agree on a political framework was set so talks over technical details on a comprehensive accord can begin ahead of a June 30 deadline.
That deadline and another one Wednesday have come and gone.
"We continue to make progress but have not reached a political understanding," said State Department spokeswoman Marie Harf. "Therefore, Secretary Kerry will remain in Lausanne until at least Thursday morning to continue the negotiations."
German Foreign Minister Frank-Walter Steinmeier told reporters Iran was expected to bring forth "new recommendations" for a possible deal, which now appears to be on shaky ground.
"Naturally, whoever negotiates has to accept the risk of collapse," Steinmeier said. "But I say that in light of the convergence that we have achieved here in Switzerland, in Lausanne, it would be irresponsible to ignore possibility of reaching an agreement."
So far negotiators have been unable to bridge a gap on what kind of research should be allowed on advanced centrifuges to enrich uranium and how quickly sanctions against Iran would be eased, The New York Times reported.
"Our friends need to decide whether they want to be with Iran based on respect or whether they want to continue based on pressure," Iranian Foreign Minister Mohammad Javad Zarif said. "They have tested the other one; it is high time to test this one"
Freshman Sen. Tom Cotton, R-Ark., -- the author of a letter sent by 47 senators to Iran saying any deal reached would only last as long as Barack Obama is president -- on Wednesday said he would like to see an outcome that would stop Iran "on all paths to getting a nuclear bomb."
He said that's possible if the United States negotiates from a position of strength.
"I don't think Iran or many of our allies or adversaries in the region take that threat of force very seriously," he said in an appearance on CNN's The Situation Room.
Leaders hope for a breakthrough after almost 18 months of negotiations over Iran's nuclear program, which Iran continues to say is peaceful. Western officials want to impose limits that would prevent Iran from producing enough material to create a nuclear weapon within a year.
Western leaders want restrictions on Iran's nuclear program for a 15-year period in exchange for a gradual easing of sanctions against the country. The number of centrifuges is also part of the negotiations, with Iran originally insisting on keeping 10,000 operating but dialing back to as low as 6,500.
Iran's economy has been hamstrung by the sanctions and the country seeks to revive crude oil exports.
In November 2013, the country secured relief from some economic sanctions and allowed limited crude oil exports in exchange for limiting its nuclear research activity. A breakthrough at the negotiating table in Switzerland would open an Iranian spigot on a market already favoring the supply side.
Iran in 2011 exported around 2.5 million barrels per day. Last year, exports averaged 1.4 million bpd. A country profile from the U.S. Energy Information Administration said Iran's ability to export crude oil is "substantially impeded" by economic sanctions.
Dan Graeber contributed to this report.