MOSCOW (AFP) — Russia on Tuesday offered to discuss with the United States allegations from Washington that it had carried out secret underground nuclear tests, in a bid to ease tensions between the world’s top two nuclear superpowers.

Russia has tested its nuclear-powered, nuclear-capable weapons systems in recent weeks, but rejects the accusation by US President Donald Trump that it had secretly detonated a nuclear device.

Trump caused concern and confusion last month when he said he was ordering the US to test its atomic weapons in retaliation for drills carried out by Russia and China — accusations rejected by both Moscow and Beijing.

None of the three countries has publicly tested a nuclear warhead since the 1990s, and all three have signed — but not ratified — the Comprehensive Nuclear-Test-Ban Treaty that bans all atomic test blasts, whether for military or civilian purposes. 

Russia’s Foreign Minister Sergei Lavrov offered on Tuesday to speak to Washington about its concerns.

“We are ready to discuss the suspicions raised by our American colleagues regarding the possibility that we might be secretly doing something deep underground,” he told state media in a televised interview.

Trump had leveled the accusations that both Russia and China had secretly tested nuclear weapons in an interview with US broadcaster CBS News earlier this month, after abruptly shelving a proposed summit with Putin on Ukraine.

Like all armed states, Russia regularly tests its delivery systems, but has rejected the accusation it has carried out unannounced weapons tests.

Lavrov said the US could check whether Russia had tested a nuclear warhead via the global seismic monitoring system. 

“Other tests, both subcritical, or those without a chain nuclear reaction, and carrier tests, have never been prohibited,” Lavrov added. 

Russia said it had not received any clarification from Washington as to the specifics of its allegations.