The United States and its allies are trying yet again to make progress in talks with Iran surrounding Tehran's nuclear program.

Diplomats met in Geneva Sunday, after high-levels talks about Iran’s nuclear ambitions were twice extended. The two sides have until March to strike some sort of an accord under the latest arrangement.

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Reuters reported Sunday that diplomats made “limited” progress in narrowing their differences during the talks, which come as some U.S. lawmakers are pushing to ramp up sanctions against Iran. The Obama administration has resisted such calls, saying new restrictions on Iran could upend ongoing negotiations.

President Obama threatened to veto new legislation that would ramp up sanctions, putting him at odds with his Democratic colleague, Sen. Robert MenendezRobert (Bob) MenendezSenate passes legislation supporting Hong Kong protesters Graham blocks resolution recognizing Armenian genocide after Erdoğan meeting Trump encounters GOP resistance to investigating Hunter Biden MORE (D-N.J.).

Sen. Lindsey GrahamLindsey Olin GrahamGraham: Report on alleged surveillance abuse in 2016 to be released Dec. 9 McConnell hopes Senate impeachment trial 'not too lengthy a process' Hillicon Valley: Progressives oppose funding bill over surveillance authority | Senators call for 5G security coordinator | Facebook gets questions over location tracking | Louisiana hit by ransomware attack MORE (R-S.C.) said Sunday he would agree to table a new sanctions bill  if Obama agreed to let Congress approve or disapprove of whatever diplomatic deal is struck with Iran.

Secretary of State John KerryJohn Forbes KerryAs Buttigieg rises, Biden is still the target Pompeo announces Israeli settlements do not violate international law Deval Patrick's 2020 entry raises stakes in New Hampshire MORE has met several times with Iranian Foreign Minister Mohammed Javad Zarif, and diplomats are continuing to meet and discuss behind closed doors.

The U.S. has entered into talks alongside France, Germany, Russia, China and England. Those allies in 2013 struck a deal with Iran in which Iran would halt progress on some of its nuclear ambitions in exchange for relief from economic sanctions.