(From left to right) Iran's Atomic Energy Organisation spokesperson Behrouz Kamalvandi, government spokesperson Ali Rabiei, and Deputy Foreign Minister Abbas Araghchi give a joint press conference at the presidential headquarters in the capital Tehran on Sunday. Photo: VCG

China on Monday urged parties related to Iran nuclear tensions to exercise restraint and solve issues through dialogue, one day after Iran announced that it would boost uranium enrichment above the cap.

"China regrets Iran's announcement to further reduce its commitments under the nuclear deal," Chinese Foreign Ministry spokesperson Geng Shuang said at a daily press briefing. 

But he pointed out that the maximum pressure on Iran by the US is the root cause of the crisis on the Iranian nuclear issue.

Iran said on Sunday it would shortly boost uranium enrichment above the cap that was set by the 2015 nuclear deal, prompting a warning from US President Donald Trump, who wants the pact renegotiated, that Tehran "better be careful."

The 2015 deal was reached between Iran and six world powers - Britain, China, France, Germany, the US and Russia - and saw Tehran agree to drastically scale down its nuclear program in exchange for sanctions relief.

"To ensure the full and effective implementation of the nuclear deal is not only the requirement of the UN Security Council resolution, but also the only realistic and effective way to solve the Iranian nuclear issue," Geng said.

Tensions between Washington and Tehran have escalated since Trump pulled the US out of the pact in May 2018 and acted to bar all international sales of Iranian oil, the country's economic lifeblood.

"The US has not only unilaterally withdrawn from the agreement, but also created more and more obstacles for Iran and others to implement the agreement through unilateral sanctions and long-arm jurisdiction," Geng said.

Iran's Atomic Energy Organization's spokesperson Behrouz Kamalvandi said on Monday that Iran has passed the 3.67 percent uranium enrichment cap and may enrich at even higher levels, according to the IRIB news agency.

"Twenty percent is not needed now, but if we want we will produce it. When we've put aside 3.67 percent enrichment we have no obstacle or problem with this action," Kamalvandi was quoted as saying.

"There is the 20 percent option and there are options even higher than that but each in its own place. Today if our country's needs are one thing, we won't pursue something else just to scare the other side a little more," he said.

"We call on all parties concerned to bear in mind the overall and long-term interests, exercise restraint, support dialogue through the joint commission mechanism and create conditions for continued maintenance and implementation of the deal," Geng said.

Kremlin spokesperson Dmitry Peskov said Monday that Russia is concerned over plans by Iran to breach the uranium enrichment cap set by the 2015 nuclear deal and will pursue diplomatic efforts to save the pact.

"The situation is of course concerning," Peskov told journalists. "Russia aims to continue dialogue and efforts on the diplomatic front. We are still supporters of the JCPOA [nuclear deal]."