With the November 24 extended deadline for the end of nuclear negotiations with Iran looming, talks in Vienna have apparently hit a rocky patch.

On Friday, Iranian Foreign Minister Mohammad Javad Zarif revealed that he would be leaving Vienna to return to Iran for consultations ahead of the looming deadline. Secretary of State John Kerry, too, announced that he was leaving the Austrian capital to travel to Paris where he would confer with his “European counterparts.”

A State Department statement revealed that Kerry’s “future travel schedule is still being finalized, and we have not yet determined when he will return to Vienna.”

French Foreign Minister Laurent Fabius and British Foreign Secretary Philip Hammond are not far behind their Iranian and American counterparts. Both will reportedly leave the city on Friday, with just hours left before the nuclear talks are due to conclude.

Radio Free Europe/Radio Liberty reported on Friday that the sticking points which might have led to the collapse of talks have to do with Iranian uranium enrichment capabilities:

In months of negotiations since an interim deal was reached a year ago, Iran’s refusal to substantially cut the output of centrifuges that can enrich uranium levels high enough to be used for nuclear weapons has been a major sticking point.

Iran denies Western accusations that its nuclear program is secretly aimed at developing a nuclear weapons capability.

But an International Atomic Energy Agency (IAEA) report on November 7 said Iran was failing to address the accusations.

As part of its probe, the IAEA has for years sought access to Parchin — a sprawling military establishment southeast of Tehran.

Republicans in Congress have fretted that the White House is behaving as though a deal with Iran has not only been reached but ratified. The National Review reported:

On Tuesday, Republican senators sent the president a letter expressing alarm about the “weak and dangerous deal” they believe the administration is negotiating and said that the administration is disregarding “clear expressions from the Senate emphasizing the need for a multi-decade agreement” that would require Iran to stop enriching uranium and fully dismantle its nuclear infrastructure.

Every Republican senator but two — Kentucky’s Rand Paul and Arizona’s Jeff Flake — signed the letter.

They may get their wish, and a deal with Iran may not be in the immediate offing. The administration suggests it has no intention to extend the deadline to conclude negotiations further, but it is unlikely the administration will allow negotiations to lapse.

UPDATE: It looks like the key negotiating partners in nuclear talks are not giving up so easily:

As evening sets in here in Vienna, neither @jzarif nor @johnkerry has left talks just yet. Negotiations continue despite expected departures

— margaret brennan (@margbrennan) November 21, 2014