On Monday, Russia said it urgently required a response from the US to its broad security demands, and warned of a possible military reaction unless political action was taken to alleviate its worries.

Last week, Moscow presented a wish list of security ideas it wants to discuss, including a guarantee from NATO to cease all military activities in Eastern Europe and Ukraine, which has alarmed the West with its force buildup near Ukraine.

Some of Russia’s plans are plainly unacceptable, according to Washington, but the US will react with more definite proposals on the framework of any discussions later this week.

A Russian official in Vienna, Konstantin Gavrilov, said ties between Moscow and NATO had reached a “moment of truth.”

“The dialogue must be serious, and everyone in NATO realizes quite well that actual political action must be made, otherwise the alternative is a military-technical and military response from Russia,” he was reported as saying by the Russian news agency RIA.

The United States’ response is likely to influence Moscow’s thinking on Ukraine, which has emerged as a major flashpoint in East-West ties.

The United States and Ukraine say Russia may be preparing an invasion of its ex-Soviet neighbor. Russia denies that and says it is Ukraine’s growing relationship with NATO that has caused the standoff to escalate. It has compared it to the 1962 Cuban missile crisis, when the world came to the brink of nuclear war.

Deputy Foreign Minister Sergei Ryabkov said that Moscow had so far received no response from the United States.

“I think they’ll try to turn this into a slow-moving process, but we need it to be urgent, because the situation is very difficult, it is acute, it tends to become more complicated,” he was quoted by RIA as saying.

The Kremlin said it was still too early to assess the West’s response, but that information from “various sources” about a readiness to discuss the ideas was positive.

Asked separately about a Belarusian proposal to host Russian nuclear weapons in the event of similar deployments in its vicinity by the West, Kremlin spokesman Dmitry Peskov said Moscow had numerous options.

“It’s no secret the deployment of different types of armaments near our borders that could pose a danger would require corresponding steps to be taken to balance the situation. There are all sorts of options here,” he said.