Delegates attend a meeting of the Joint Commission of the Joint Comprehensive Plan of Action (JCPOA) in Vienna, Austria, on July 28, 2019. (Xinhua/Guo Chen)

All sides have expressed their strong opposition against the U.S. unilateral imposition of sanctions, as the remaining signatories of the Iran nuclear deal meet in Vienna.

VIENNA, July 29 (Xinhua) -- The remaining Iran nuclear deal signatories reaffirmed their commitment to the Joint Comprehensive Plan of Action (JCPOA) and criticized the United States for its unilateral sanctions during a meeting here Sunday, according to a Chinese delegate.

"All sides have expressed their strong opposition against the U.S. unilateral imposition of sanctions, especially the extraterritorial application of the sanctions," said Fu Cong, director general of the Department of Arms Control at the Chinese Foreign Ministry, at a press conference following the meeting.

"And they also expressed support and appreciation of China's efforts to implement the JCPOA, in particular China's effort to maintain normal trade and oil relations with Iran," Fu said.

Fu Cong (C), head of the Chinese delegation, is seen before the International Atomic Energy Agency (IAEA) Board of Governors meeting in Vienna, Austria, July 10, 2019.(Xinhua/Guo Chen)

Iran's senior nuclear negotiator Abbas Araqchi called the talks "constructive."

"Discussions were good. I cannot say that we resolved everything. I can say there are lots of commitments," Araqchi added.

The meeting was convened at the request of France, Germany, Britain and Iran to examine issues linked to the implementation of the JCPOA in all its aspects, according to diplomatic sources based in Vienna.

At the meeting, China urged the three European countries to expand INSTEX, a payment system to facilitate trade between the EU and Iran to get around U.S. sanctions, and open it up to third countries, said Fu.

There were tense moments but on the whole the atmosphere was "professional," he said.

There was a general agreement that a foreign minister's meeting may be held, but more preparations are needed for this meeting to happen, Fu said.

Iranians celebrate the nuclear agreement in Tehran, Iran on July 14, 2015. (Xinhua/Ahmad Halabisaz)

The JCPOA was inked in 2015 between Iran and the United States, France, Russia, Britain, Germany, Russia and China. Washington unilaterally withdrew from the landmark deal last year and resurrected sanctions on Teheran.