(Reuters) - A possible resumption of nuclear weapons tests by Moscow remains an open question in view of hostile U.S. policies, a senior Russian diplomat was quoted as saying early on Saturday.
"This is a question at hand," Deputy Foreign Minister Sergei Ryabkov told TASS news agency when asked whether Moscow was considering a resumption of tests.
"And without anticipating anything, let me simply say that the situation is quite difficult. It is constantly being considered in all its components and in all its aspects."
In September, Ryabkov referred to President Vladimir Putin as having said that Russia would not conduct a test as long as the United States refrained from carrying one out.
Moscow has not conducted a nuclear weapons test since 1990, the year before the collapse of the Soviet Union.
But Putin this month lowered the threshold governing the country's nuclear doctrine in response to what Moscow sees as escalation by Western countries backing Ukraine in the 33-month-old war pitting it against Russia.
Under the new terms, Russia could consider a nuclear strike in response to a conventional attack on Russia or its ally Belarus that "created a critical threat to their sovereignty and (or) their territorial integrity".
The changes were prompted by U.S. permission to allow Ukraine to use Western missiles against targets inside Russia.
Russia's testing site is located on the remote Novaya Zemlya archipelago in the Arctic Ocean, where the Soviet Union conducted more than 200 nuclear tests.
Putin signed a law last year withdrawing Russia's ratification of the global treaty banning nuclear weapons tests. He said the move sought to bring Russia into line with the United States, which signed but never ratified the treaty.