The tensions are high among negotiators as the Iran nuclear talks continue in overtime, but a deal remains elusive. In the latest development, Iran is blaming bickering between the U.S., Russia and China for the latest missed deadline on Thursday in Vienna, saying that negotiators are backtracking.

Iran Says US-Russia Bickering Hurting Nuclear Talks

A senior Iranian official noted very late Thursday that the U.S. and other countries in the talks had modified their positions, in effect backtracking from agreements made earlier. He said these countries were bickering over how and when to remove some sanctions against Tehran.

The anonymous official commented he could not tell these differences were just a “glitch” or a major setback in the nuclear talks, but this backtracking was the real reason the most recent deadline had been missed.

More on Iranian claim of U.S. backtracking

The Iranian official pointed out that the backtracking started ob Wednesday night, coincidentally at the same time as the arrival of several European ministers and a conference call between President Obama and the Secretary of State Kerry and other senior U.S. negotiators.

According to the official, on Thursday night the U.S., European, Russian and Chinese negotiators began to express differences of opinion on issues including the reopening some of the nuclear topics that have been debated for months, to the duration of current sanctions on Iran.

He continued to say that both Russia and China had disagreed with rest of the countries at the negotiating table (U.S., France, Britain and Germany), and supported Tehran’s contention that a UN arms embargo against Iran should be removed given a final, binding nuclear agreement.

Friday meeting between Kerry and Zarif

Of note, Kerry, Iranian FM Mohammad Javad Zarif and a senior EU official had a private meeting Friday afternoon. Zarif told the media following the meeting that he and the other negotiators would apparently remain in Vienna over the weekend.

Lifting of Iran arms embargo is key sticking point

Russian FM Lavrov made it obvious in a series of tweets that he felt Iran was at blame for the missed deadline and the arms embargo should be lifted, “especially since Iran is persistently supporting the fight against ISIS and the elimination of this threat in the region.”

Moreover, a senior Iranian diplomat claimed China felt the same way, but the Chinese Ministry of Foreign Affairs refused confirm the government’s position on the arms embargo on Iran.

The U.S. insists the arms embargo must remain separate the nuclear talks, and American officials have noted off the record that the Russian and Chinese interest in ending the arms embargo relates directly to plans to sell Iran billions of dollars worth of weapons.

U.S. says will not “rush” a deal

Kerry said in remarks on Wednesday that negotiators would not rush a deal, but by the same token, the U.S. would not  “sit at the negotiating table forever.”

“Given that the work here is very technical and that the stakes are very, very high, we will not rush and we will not be rushed,” Kerry commented. “But as I have said many times — and as I discussed with President Obama last night — we are not going to sit at the negotiating table forever. We also recognize that we shouldn’t get up and leave simply because the clock strikes midnight.”