The Kremlin on Thursday reacted cautiously to President Donald Trump's remarks about the resumption of nuclear weapons testing by the United States, saying that Russia had not tested but that Moscow would follow suit if Washington did.

Trump ordered the U.S. military on Thursday to immediately resume testing nuclear weapons after a gap of 33 years, minutes before beginning a meeting with Chinese President Xi Jinping.

Trump said that because of "other countries testing programs" the United States would start testing "on an equal basis."

"President Trump mentioned in his statement that other countries are engaged in testing nuclear weapons. Until now, we didn't know that anyone was testing," Kremlin spokesman Dmitry Peskov told reporters.

Russia, he said, had received no prior notification from the United States about a change to Washington's position on nuclear testing.

Asked if the Kremlin felt that a new nuclear arms race had been triggered by Trump's remarks, Peskov said: "Not really."

Peskov underscored that Russia's test of the Burevestnik cruise missile on Oct. 21 and the Poseidon nuclear-powered super torpedo on Oct. 28 were most definitely not nuclear weapons tests.

Putin, who commands the world's biggest nuclear arsenal, has repeatedly said that if any country tests a nuclear weapon then Russia will do so too.

"I want to recall President Putin's statement, which has been repeated many times: if someone departs from the moratorium, Russia will act accordingly," Peskov said.

Post-Soviet Russia has never tested a nuclear weapon. The Soviet Union last tested in 1990, the United States last tested in 1992 and China in 1996.