China called upon parties related to the Iran nuclear deal to exercise restraint and strengthen dialogue on Wednesday amid escalating tensions over the issue.

Noting that China commended Iran for strictly implementing the nuclear deal so far, Foreign Ministry spokesman Geng Shuang said at a daily news conference that China has been in close communication with Iran and other related parties.

Iranian President Hassan Rouhani said on Wednesday in letters to five world leaders that Iran will scale back its compliance with the 2015 nuclear agreement in 60 days unless they keep their promises on the deal.

Rouhani said Iran will increase its uranium enrichment level and get ready for talks with Europe on the Joint Comprehensive Plan of Action, in which wide-ranging sanctions on the Iranian economy were lifted and Teheran in return agreed to accept limits on its nuclear technology program and allow inspections of its nuclear installations.

Iran said earlier that it would announce a set of retaliatory measures on Wednesday in response to the US withdrawal from the 2015 nuclear deal and the reimposition of sanctions on Teheran. US President Donald Trump pulled Washington out of the Iranian international nuclear deal in May 2018 and resumed energy and financial sanctions against the country.

Geng said that China firmly opposes the unilateral US sanctions and so-called long-arm jurisdiction against Iran, and that it regrets that such practices have escalated tensions on the Iranian nuclear issue.

The Joint Comprehensive Plan of Action is a multilateral agreement endorsed by the United Nations Security Council, and it is vital for the international nonproliferation regime as well as peace and stability in the Middle East, he said.

China will maintain communication with related parties and make efforts to continue safeguarding and implementing the agreement, and will also safeguard the legitimate rights of Chinese enterprises, he added.

Before the president's letters, Iranian Foreign Minister Mohammad Javad Zarif said that Teheran has decided to stop implementing some of its commitments related to the nuclear agreement, the official IRNA news agency reported on Wednesday.

Xinhua contributed to this story.