UPDATE 1-Russia's Lavrov says work under way on Putin's order on possible Russian nuclear test

Russian Foreign Minister Sergei Lavrov said on Saturday that work is under way on President Vladimir Putin's order to prepare proposals for a possible Russian nuclear test, state news agency TASS reported.

According to TASS, Lavrov said: "Regarding President Vladimir Putin's instruction at the Security Council meeting on November 5, it has been accepted for implementation and is being worked on. The public will be informed of the results." The order was in response to President Donald Trump's surprise announcement last week that the U.S. would resume testing.

TASS also cited Lavrov as saying that Russia had received no clarification from the U.S. regarding Trump's order. Russia-U.S. relations have deteriorated sharply in the past few weeks as Trump, frustrated with a lack of progress towards ending the war in Ukraine, has cancelled a planned summit with Putin and imposed sanctions on Russia for the first time since returning to the White House in January.