VIENNA, June 28 (Xinhua) -- China is fully committed to the Joint Comprehensive Plan of Action (JCPOA), said a Chinese delegate after a three-hour meeting of Iran, Russia, China, Britain, France and Germany here on Friday.

Fu Cong, director general of the Department of Arms Control of the Chinese Foreign Ministry stressed that China categorically rejects U.S. "zero-tolerance policy" on Iran oil sales, and is willing to do everything it can to maintain legitimate economic and trade relations with the country and safeguard economic interests of Chinese companies.

China will also go forward at full speed with respect to the Arak nuclear reactor project, Fu said. The Chinese-led initiative to redesign Iranian heavy water reactor in Arak is aimed at minimizing its plutonium production and avoid production of weapons-grade plutonium.

During the meeting, Iran has sent a "clear and loud" message that it will stay in the JCPOA, commonly known as the Iran nuclear deal, Fu said.

Delegates expressed sympathies over situations in Iran and condemned U.S. unilateral withdrawal from the agreement, he said, adding that the "maximum pressure" against Iran is the root cause of all tensions surrounding the issue.

The Instex, a financial instrument designed to help European companies trade with Iran while avoiding U.S. sanctions, is finally "operational", said Fu. And it was agreed on Friday's meeting that working groups will be set up to explore how to deal with the excess of the production of low-grade uranium by Iran.

U.S. President Donald Trump decided last year to pull the United States out of the 2015 multinational accord and has re-imposed sanctions against Iran while Iran has begun going back on the agreement.

In May, Iran announced that it would begin accumulating more low-enriched uranium, but it has not yet followed through the threat that it would breach the deal's cap on stockpiles of the material.

Russia and the three EU countries have urged Iran to fully comply with the JCPOA, said Fu.