TEHRAN, Iran (AP) — Tehran says that China has slowed down working on its redesign of a heavy water reactor in Iran, following the U.S. withdrawal from Tehran's nuclear agreement with world powers.

Ali Akbar Salehi, head of Iran's nuclear agency, was quoted by state-run news agency IRNA as saying that "the Chinese side decreased the speed of cooperation with us despite their commitments." He says Iran has "alternative" choices if China cannot not fulfil its job. Salehi speculates that Beijing fears possible sanctions by the U.S. if it continues cooperation with Iran but did not elaborate further.

Under the 2015 nuclear agreement, experts from the United States and China were to help Iran redesign the Arak heavy water nuclear reactor to limit the amount of plutonium it produces as a byproduct.