Russian Deputy Foreign Minister Sergei Ryabkov said today that the United States could face “fatal consequences,” if they do not heed Moscow’s warnings not to let Ukraine use weapons supplied by Washington to strike targets inside Russia.

Ryabkov was commenting on the decision he made President Joe Bidenlast week to authorize the use of arms that Ukraine received from the US to strike targets inside Russia involved in attacks in Ukraine’s Kharkiv province.

“I would like to warn American leaders not to make miscalculations that could have fatal consequences. For unknown reasons, they underestimate the seriousness of the response they may receive,” Ryabkov said, according to the RIA news agency.

He was referring to comments made last week by President Vladimir Putin, who said that NATO countries are playing with fire and risk triggering a deeper global conflict — a series of warnings from Moscow about the risk of serious escalation.

“I invite these persons (in the US) … to spend some of their time, which they apparently spend on some kind of video game, judging by the lightness of their approach, to study in detail what is being said by Putin,” said Ryabkov.

Putin has addressed “a very important warning and it must be taken [υπόψη] with the utmost seriousness,” he added.

Putin said the West would be directly involved with Ukraine using its weapons to strike deep inside Russian territory because those attacks would require the help of its satellites, intelligence services and military.

NATO Secretary General Jens Stoltenberg said last week that NATO has a right to help Ukraine to support its right to defend itself and that this does not make NATO a party to the conflict.

According to Russian news agencies, Ryabkov said attempts by Kiev to attack Russian early warning radar systems would be countered and that Moscow could respond asymmetrically to such moves.

A source in Kiev’s intelligence services said last week that a Ukrainian drone targeted a long-range radar deep inside Russian territory that is part of Russia’s nuclear early warning system.

In addition, the Russian Foreign Ministry said that discussions about whether to allow Ukraine to use Patriot air defense systems over Russian territory show that the West is on a path of escalation, according to the TASS news agency.

Russia will take all measures to prevent such threats, the Russian Foreign Ministry said.