MOSCOW — Russia may take unspecified new measures to ensure its security if the U.S. and its allies continue to take provocative action and ignore Moscow's demand for guarantees precluding NATO's expansion to Ukraine, a senior diplomat said Saturday.

Deputy Foreign Minister Sergei Ryabkov accused Western allies of continuously pushing the envelope in relations with Russia, and warned that Moscow could also up the ante if the West doesn't treat its demands seriously.

Ryabkov's statement in an interview with the Interfax news agency came a day after Moscow submitted draft security documents demanding that NATO deny membership to Ukraine and other former Soviet countries and roll back the alliance's military deployments in Central and Eastern Europe — bold ultimatums that are almost certain to be rejected by the U.S. and its allies.

The publication of the demands — contained in a proposed Russia-U.S. security treaty and a security agreement between Moscow and NATO — comes amid soaring tensions over a Russian troop buildup near Ukraine that has raised fears of an invasion. Russia has denied it has plans to attack its neighbor but wants legal guarantees that would rule out NATO expansion and deploying weapons there.

Russian President Vladimir Putin raised the demand for security guarantees in last week's video call with U.S. President Joe Biden. During the conversation, Biden voiced concern about a buildup of Russian troops near Ukraine and warned him that Russia would face "severe consequences" if Moscow attacked its neighbor.

"They have been extending the limits of what's possible" regarding Russia, Ryabkov told Interfax in response to a question about the Western threat of tough new sanctions against Moscow.

"But they fail to consider that we will take care of our security and act in a way similar to NATO's logic and also will start extending the limits of what is possible sooner or late," Ryabkov said. "We will find all the necessary ways, means and solutions needed to ensure our security."

He didn't elaborate on what action Russia may take if its demands are rejected by the West.

NATO Secretary-General Jens Stoltenberg emphasized Friday that any security talks with Moscow would need to take into account the trans-Atlantic alliance's concerns and involve Ukraine and other partners. The White House similarly said it's discussing the proposals with U.S. allies and partners, but noted that all countries have the right to determine their future without outside interference.

Ryabkov said that NATO's moves have become increasingly provocative, describing them as "balancing on the edge of war." He added that Russia now wants to hear a Western response before upping the ante.

"We don't want a conflict. We want to reach an agreement on a reasonable basis," he said. "Before making any conclusions what to do next and what steps could be taken, we need to make sure that the answer is negative. I hope that the answer will be relatively constructive and we engage in talks."

He said that the deployment of NATO's troops near Russia in the Baltic and Black Sea regions have challenged Russia's core security interests, adding that "no one should underestimate Moscow's resolve in protecting its national security interests."

Russia annexed Ukraine's Crimean Peninsula in 2014 and shortly after cast its support behind a separatist rebellion in the country's east. More than seven years of fighting has killed over 14,000 people and devastated Ukraine's industrial heartland, known as the Donbas.

Copyright 2021 NPR. To see more, visit https://www.npr.org.