VIENNA, April 23 (Xinhua) -- China and Iran signed the first commercial contract to redesign Iran's Arak heavy water reactor in Vienna on Sunday.

Representatives from China and Iran sign the first commercial contract to redesign Iran's Arak heavy water reactor in Vienna, Austria, on April 23, 2017. Redesigning the Arak heavy water reactor is a core aspect of the Joint Comprehensive Plan of Action (JCPOA) on Iran's nuclear program. (Xinhua/Wang Tengfei)

The commercial contract signed between the two sides is seen as an important step towards modification of the Arak heavy water reactor.

Under the Joint Comprehensive Plan of Action (JCPOA), Iran agreed to redesign the reactor to minimize its plutonium production and avoid production of weapons-grade plutonium.

Redesigning the Arak heavy water reactor is a core aspect of the 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 States and 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.

Iranian ambassador to the International Atomic Energy Agency (IAEA) Reza Najafi told Xinhua the signing of the contract is important and Iran has very good cooperation with China. He said it's the example cooperation which the other sides should learn from.