"China and Iran are enjoying good relations in the political, economic, industrial, investment, and energy sectors, and bilateral ties are expected to step forward after the meeting between Chinese President Xi Jinping and Iranian President Hassan Rouhani," Khaji told the Global Times on Saturday.
China was the first destination of Iran's foreign minister after the US pullout, showing that Iran expects China to play a "major and constructive" role in saving the JCPOA, he said.
"China has played a very positive and fair role in the negotiations. After the deal was reached, China has been truthful in implementing the landmark deal," Khaji added.
After the US pulled out of JCPOA, China reaffirmed that it would remain in the deal and oppose any unilateral sanctions against Iran, he said.
Iran is also negotiating with other nations involved to keep the deal alive, and will stay committed to it if its core interests are secured, said Khaji, adding that the deal can work without the US.
"If the other members can guarantee and ensure Iran's core interests and advantages in the deal, Iran will stay (in the deal)," said the ambassador.
Rouhani is in China for a working visit as well as the annual Shanghai Cooperation Organization (SCO) summit over the weekend in the Chinese coastal city of Qingdao in Shandong Province. Iran is an observer member of the SCO.
Rouhani's visit comes after the US declared on May 8 that it would withdraw from the Iran nuclear deal, formally known as the Joint Comprehensive Plan of Action (JCPOA). Iran said it would continue to honor the deal as long as the other five JCPOA signers remained committed to it.