The White House on Friday said the United States and its negotiating partners “have never been closer” to an agreement with Iran in ongoing nuclear talks.

The more upbeat remarks from the US camp follow a period in which tensions have crept into the talks, with diplomats warning they could walk out or positioning themselves to blame the other side in the event of a breakdown.

Khamenei was quoted as saying: “Fighting global arrogance is the core of our revolution and we can not put it on hold”.

“The United States is flawless instance of Arrogance”. America is the quintessential arrogant power.

His comments were a possible blow to USA hopes that an agreement will lead to improved bilateral relations that could translate into increased cooperation in a common cause – the fight against Islamic radicals.

But nearly immediately after the top United States diplomat emerged from nearly 90 minutes of fresh talks yesterday with Zarif and European Union foreign policy chief Federica Mogherini, he tweeted that things remained tough.

Zarif’s words came on Friday as he spoke to reporters from a balcony outside the venue of the nuclear talks in Vienna, Austria.

It remained unclear whether Russian Foreign Minister Sergei Lavrov would return on Saturday. French foreign minister Laurent Fabius has been the most hawkish negotiator.

The Chinese and Russian foreign ministers have said they will go to Vienna if a deal appears close. “Hopeful”, Kerry said, calling his latest meeting with Zarif “positive”.

While Iranian officials relished in what they considered diplomatic progress, Kerry, however, expressed via Twitter that the two sides still have some “difficult issues” to resolve. Since the start of the current round, he has said twice that the negotiations couldn’t be open-ended and warned that the US was prepared to call an end to the talks. The practice amounts to “psychological war”, Ali Akbar Velayati, a senior adviser to Khamenei, said Friday, according to the Iranian Students News Agency.

“The president has indicated to his negotiating team that they should remain in Vienna and should continue to negotiate as long as talks continue to be useful”, White House spokesman Josh Earnest told reporters.

Any deal is meant to clamp long-term and verifiable restrictions on Iranian nuclear programs that are technically adaptable to make weapons in exchange for sanctions relief for Tehran.

A new headache emerged in recent days, when the Iranian delegation insisted that a United Nations arms embargo must be lifted once a deal is reached, something that Western countries are wary about given Iran’s alleged role in several Middle East conflicts. The cuts would ensure a “breakout” time of more than a year before Iran would have sufficient enriched uranium for a nuclear weapon. But, there are still some issues that have to be resolved.

Iranians rallied for the last Friday of the fasting month of Ramadan, observed in Iran as “Qods Day” or “Death to Israel day”, to show support for Palestinians, protest against Israel and chant slogans against the “Great Satan” United States.

The negotiators missed a Friday morning deadline set by the US Congress for an expedited 30-day review of the deal.

“We’re pushing”, said Kerry when asked if there would be a deal this weekend.

After more than two weeks of intense and often combative talks that blew through three deadlines in Vienna and a weekend of deadlock, diplomats expressed optimism that a deal was at hand.

Secretary of State John Kerry on Saturday said progress remains slow on reaching a final agreement with Iran over its nuclear arms research.