Moscow, Russia - Russia on Thursday sought to cool rising nuclear tensions with the US, after recent tests of nuclear-capable weapons systems prompted President Donald Trump to order his own tests.

The Kremlin said its recent testing of nuclear-powered and nuclear-capable weapons – the Burevestnik cruise missile and the Poseidon underwater drone – did not constitute a direct test of an atomic weapon.

Both countries observe a de facto moratorium on testing nuclear warheads, though Russia regularly runs military drills involving systems that are capable of carrying such weapons.

"Regarding the tests of Poseidon and Burevestnik, we hope that the information was conveyed correctly to President Trump," Kremlin's spokesperson Dmitry Peskov told journalists, including AFP, during a daily briefing.

"This cannot in any way be interpreted as a nuclear test," he insisted.

Trump said Thursday he was ordering the Pentagon to restart tests as a response to actions by other states.

"Because of other countries testing programs, I have instructed the Department of War to start testing our Nuclear Weapons on an equal basis," he said Thursday in a social media post.

But it was not immediately clear if Trump was referring to testing nuclear warheads – something the United States last did in 1992 – or testing weapons systems capable of carrying atomic warheads.

The Kremlin implied Thursday that it would also test nuclear warheads if Trump ordered a live test of an atomic weapon.

"If someone departs from the moratorium, Russia will act accordingly," Peskov said.

Russian President Vladimir Putin has repeatedly said if the US started testing nuclear weapons again, Russia would follow suit.

In 1996, the two countries signed – but have not ratified – the Comprehensive Nuclear-Test-Ban Treaty, which bans all atomic test blasts, whether for military or civilian purposes.