He made the remarks in a news conference today (Tuesday) in response to a question from a Xinhua reporter.
He also hoped that today's JCPOA meeting would end in the removal of anti-Iranian sanctions.
"Currently, Iran's nuclear deal is at an important stage," the official said, "China welcomes the JCPOA meeting to discuss issues related to the lifting of US sanctions and Iran's return to its commitments."
Criticizing Washington's unilateral sanctions against the Islamic Republic, he continued: "Beijing also supports talks between JCPOA members and the US in a proper way and we hope that all parties will reach a consensus on the plan to return the United States and Iran to their commitments."
"What I want to emphasize is that the unilateral withdrawal of the United States from the JCPOA undermined the agreements of all members of this nuclear agreement, and this is the root cause of the current crisis over Iran's nuclear program."
"The United States must return to the JCPOA unconditionally, lift all illegal sanctions against Iran, and abandon its use of force against other parties," he noted.
"While defending its legal rights and interests, China has always played a constructive role on the issue of Iran's nuclear program and continues to strive to get the JCPOA back on track as quickly as possible," Lijian added.
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