According to Chinese official media, President Xi Jinping of China called for the swift and appropriate resolution of the Iran nuclear issue on Tuesday while also pledging his support for the Islamic Republic in defending its rights and interests.

Xi assured Iran’s President Ebrahim Raisi during talks in Beijing that China would continue to “participate constructively” in discussions to restart negotiations on putting the Iran nuclear deal into effect.

A 2015 nuclear agreement limited Iran’s uranium enrichment programme to make it harder for Tehran to develop nuclear arms, in return for lifting international sanctions. Iran says it was further developing nuclear energy for peaceful reasons.

But in 2018 then-U.S. President Donald Trump ditched the deal, saying it had not done enough to curb Tehran’s nuclear activities, and reimposed sanctions.

China has criticised Washington for withdrawing from the deal and insists that the United States should make the first move in reviving the pact.

In September, the United States imposed new sanctions on companies involved in Iran oil exports, including five based in China. Washington said it would continue enforcing sanctions on Iran’s oil and petrochemical sales so long as Tehran continues to accelerate its nuclear program.

Ahead of his three-day visit that started on Tuesday, Raisi wrote an editorial in China’s state-controlled People’s Daily in which he said both countries believe that unilateralism and “violent” measures such as the imposition of “unjust” sanctions are the main causes of crises and insecurity in the world.

In the editorial, Raisi described China as an “old friend”, and said Iran’s efforts to strengthen relations would be unaffected by regional and international situations.

“No matter how the international and regional situation changes, China will unwaveringly develop friendly cooperation with Iran and promote the continuous development of the China-Iran comprehensive strategic partnership,” Xi said.

China said it is willing to deepen cooperation with Iran in trade, agriculture, industry and infrastructure as well as to import more high-quality Iranian agricultural products.

Xi and Raisi pledged to forge a stronger alliance when they last met in person on the sidelines of the Shanghai Cooperation Organisation summit in the Uzbek city of Samarkand in September.

Last year, Iran and China also began the implementation phase of a 25-year cooperation accord under which China is to invest billions of dollars in Iran’s petroleum sector in exchange for the supply of oil and petrochemical products. China is already Iran’s biggest trading partner.

The pact was originally proposed by Xi on his visit to Iran in 2016.