As the Friday deadline looms the negotiators on Tehran’s nuke deal seem to be in deadlock, with the US reportedly refusing to accept Iran's rights, particularly concerning the relief from sanctions.

"While the Iranian team is showing flexibility, the Americans are refusing to accept Iran's obvious right, particularly on sanctions," a source told Iran's semi-official Fars news agency on Thursday evening.

The West has “toughened its stance within last few hours, and in a clear U-turn even refuses to accept Iran's nuclear rights," an unnamed source told Iranian State TV.

The Islamic republic and six major powers – the US, Britain, France, Russia, China and Germany – for the past few months have been negotiating on Iran’s right to enrich uranium for peaceful purposes in turn for relief from sanctions.

The deadline for the final deal has been postponed several times after the framework of the agreement was set up in Swiss Lausanne on April 2.

As the talks have reached a crucial stage on Thursday, US Secretary of State John Kerry signaled that an agreement may not be confirmed before the deadline expires after all.

“We will not rush and we will not be rushed” while “tough issues” are still on the table, Kerry said speaking to reporters in Vienna, the scene of the deadlocked negotiations.

Continuing to discuss difficult issues this AM. Working diligently to see if agreement possible. #IranTalksViennapic.twitter.com/xrrX9hhRFL — John Kerry (@JohnKerry) July 9, 2015

The White House, in turn, issued a statement saying that the negotiations can continue for as long as the parties are committed to resolving the issues.

“As long as there's tangible evidence that there's a constructive effort under way then the talks will continue," said White House spokesman Josh Earnest at a press briefing on Thursday.

On the other hand, Washington gave hope of an impending decision, saying that the negotiations are not likely to drag on for “many more weeks.”

Previous reports suggested that the deadline for reaching a deal may be extended to July 13.

It seems vital to complete the negotiation process by the end of Thursday Washington time, as under US law, if a full accord is failed to be submitted to Congress before the deadline, the US lawmakers have to double the review period to 60 days, during which the president’s administration cannot waive sanctions on Iran.

#IranTalks This is the time. Never been so close but historical decisions have to be taken @FedericaMog@camanpourpic.twitter.com/bAZdgGjInq — Catherine Ray (@CatherineEUspox) July 9, 2015

With the rising level of impatience in the air, European Union foreign policy chief Federica Mogherini said that the negotiators will continue conceding details of the historic nuclear deal past a deadline for a long-term agreement, which to expire on Tuesday.

“The price of any mistake grows, and it’s really hard to calculate and predict when the final day of the talks will be,” said Russia’s Deputy Foreign Minister Sergey Ryabkov. “For the moment I will refrain from naming any particular day … it can happen at any given moment.”