(Bloomberg) -- Iran’s latest proposals on how to restore a nuclear deal with world powers sharply divided negotiators at talks in Vienna, and could even threaten to dull the diplomatic support it has received from its staunchest ally in Beijing. 

Despite China’s ties to Tehran and its role as a key player in negotiations to revive the 2015 agreement, the Islamic Republic appears close to breaching even some of Beijing’s limits after serious problems emerged in the course of talks that ended Friday.

“The Iranian colleagues came up with a written revision to the text we left in June,” said Chinese envoy Wang Qun, adding that the changes left the sides far from a solution and risked bogging down diplomacy. “China continues to facilitate the process by trying to work together in partnership with our Russian colleagues to bring all these parties together.”

The discussions in Vienna this week, the first since a hardline administration took over in Iran, ended and the U.S. team led by envoy Rob Malley is returning to Washington, White House Press Secretary Jen Psaki said Friday. Iran did “not come to Vienna with constructive proposals,” she added. 

The stalemate risks spiraling out of control unless Iran reconsiders its positions, according to European diplomats, who asked not to be identified in line with established rules. They suggested China and Russia are urging Tehran to reconsider demands that could set talks back months, an assertion U.S. Secretary of State Antony Blinken echoed during a conference on Friday. 

“Even Russia and China are clearly frustrated with what Iran is doing or not doing in these talks,” Blinken said during a panel at the Reuters NEXT conference. “So Iran has some very important decisions to make.”

Among the most contentious Iranian positions was the insistence that its engineers be allowed to continue using some advanced centrifuges that weren’t permitted under the original agreement, according to one of the European officials.

Tehran’s government is also seeking broader respite from sanctions than the U.S. is prepared to give, as well as guarantees that future White House administrations won’t again scuttle the accord. 

“Some proposals by Iran are inconsistent with the JCPOA and some go beyond the provisions of the JCPOA,” read a statement by European diplomats, referring to the name of their 2015 agreement with Iran. “Tehran is walking back almost all of the difficult compromises crafted after many months of hard work.”

Iran’s lead negotiator, Ali Bagheri Kani, confirmed Tehran’s proposals focused on removing U.S. sanctions and how it intends to roll back advances in nuclear activities, saying they reflect its serious intent at the negotiations. 

Amid this week’s talks, International Atomic Energy Agency monitors confirmed Iran had begun enriching uranium to higher levels at an underground plant in Fordow. Inspectors remain frozen out of an Iranian workshop that produces parts for the fast-spinning machines that separate uranium isotopes. The nuclear deal gave IAEA special dispensations that go beyond their normal accounting of uranium stockpiles.

The deadlock in Vienna could increase Middle East tensions and result in more saber rattling among nations concerned by Iran’s atomic activities. Energy markets have been closely watching the talks for signs of when the holder of the world’s No. 2 gas and No. 4 oil reserves might return to global markets.

“We have identified the challenges we have ahead. Now it’s time to consult with capitals,” the EU’s Enrique Mora told reporters in Vienna. “Time is limited, there is a sense of urgency.”

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Speaking in Dubai on Friday, French President Emmanuel Macron suggested that parties to the agreement may also need to consult more with Middle Eastern nations, some of which are rivals of Iran and strident critics of the 2015 deal. 

“It is very difficult to find a deal if Gulf countries, Israel and all those who are directly affected in their security, aren’t part of it,” he said. “Their interests need to be taken into account and they need to be heard. And in order to have efficiency in our treatment, we must have a coordinated proposal, at least with China.”

Blinken previous offered some his most downbeat remarks about prospects for a new deal, telling reporters Thursday “we will not accept the status quo of Iran building its program on the one hand and dragging its feet on the other. That’s not going to last.”

Represenatives from all sides are expected to reconvene next week in Vienna to continue the talks. 

(Adds Blinken and Psaki comments starting in fourth paragraph.)

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