BEIJING, April 20 (Xinhua) -- China and Iranwill sign the first commercial contract to redesign Iran's Arak heavy water reactor in Vienna on Sunday, a Foreign Ministry spokesman said on Thursday.

China and Iran have reached initial agreement on the commercial contract, Spokesman Lu Kang said at a daily news briefing.

Redesigning the Arak heavy water reactor is a core aspect of the Joint Comprehensive Plan of Action (JCPOA) on Iran's nuclear program. The JCPOA was reached in Vienna in July 2015 between Iran and the P5+1 group, namely Britain, China, France, Russia, the United Statesand Germany.

The P5+1 countries have created a working group led by China and the United States to work with Iran to redesign the reactor, said Lu.

The signing will create a favorable condition for the progress of the redesign. "China will do the follow-up work with all parties involved in accordance with the comprehensive nuclear deal and the consensus reached by all parties," Lu said.

The 7th Joint Commission between Iran and the P5+1 will convene in Vienna next Tuesday. Lu said the contract between China and Iran will inject positive impetus to the meeting.

"China hopes all parties will maintain their political will and properly handle differences to implement the agreement and contribute to the international nuclear non-proliferation regime and the peace and stability of the Middle East," Lu added.