MOSCOW (AP) — A senior Russian diplomat says Moscow and Washington are running out of time to extend the last remaining nuclear arms control treaty.

Vladimir Leontyev, deputy head of the Russian Foreign Ministry's arms control department, said Friday that "it's clear that we won't be able to produce a full-fledged replacement" to the New START treaty that expires in 2021. He said that Russia-U.S. talks over the past year have shown that "there are issues that require very serious examination on expert level."

Leontyev said Russia's prospective Sarmat intercontinental ballistic missile and Avangard hypersonic glide vehicle fall under the pact, but other new weapons announced by President Vladimir Putin don't, including the Poseidon nuclear-armed underwater drone, the Burevestnik nuclear-powered cruise missile and the Kinzhal hypersonic missile.

He said the U.S. sees things differently, raising the need for new, complex talks..