Earlier this month, Moscow submitted draft security documents demanding that NATO deny membership to Ukraine and other former Soviet countries and roll back its military deployments in Central and Eastern Europe.

The Kremlin presented its security demand amid tensions over a Russian troop buildup near Ukraine in recent weeks that has fueled Western fears of a possible invasion. U.S. President Joe Biden warned Putin in a video call earlier this month that Russia will face “severe consequences” if it attacks Ukraine.

Russia has denied an intention of launching an invasion and, in its turn, accused Ukraine of hatching plans to try to reclaim control of the territories held by Moscow-backed rebels by force. Ukraine has rejected the claim.

Putin has urged the West to move quickly to meet his demands, warning that Moscow will have to take “adequate military-technical measures” if the West continues its “aggressive” course “on the threshold of our home.”

Asked to specify what such Moscow’s response could be, he said in comments aired by Russian state TV Sunday that “it could be diverse,” adding that “it will depend on what proposals our military experts submit to me.”

The U.S. and its allies have refused to offer Russia the kind of guarantee on Ukraine that Putin wants, citing NATO’s principle that membership is open to any qualifying country. They agreed. however, to launch security talks with Russia next month to discuss its concerns.

Putin said the talks with the U.S. will be held in Geneva. In parallel, negotiations are also set to be held between Russia and NATO and broader discussions are expected under the aegis of the Organization for Security and Cooperation in Europe.

In remarks broadcast Sunday, Putin said Russia submitted the demands in the hope of a constructive answer from the West.

“We didn’t do it just to see it blocked … but for the purpose of reaching a negotiated diplomatic result that would be fixed in legally binding documents,” Putin said.

He reaffirmed that NATO membership for Ukraine or the deployment of alliance weapons there is a red line for Moscow that it wouldn’t allow the West to cross.

“We have nowhere to retreat,” he said, adding that NATO could deploy missiles in Ukraine that would take just four or five minutes to reach Moscow. “They have pushed us to a line that we can’t cross. They have taken it to the point where we simply must tell them; ‘Stop!’”

He voiced concern that the U.S. and its allies could try to drag out the security talks and use them as a cover to pursue a military buildup near Russia.

He noted that Russia published its security demands to make them known to the public and raise the pressure on the U.S. and its allies to negotiate a security deal.

Putin’s spokesman Dmitry Peskov said in remarks broadcast Sunday that NATO’s expansion to Ukraine or other ex-Soviet nations is “a matter of life or death for us.”

He noted that Friday’s test-firing of Russia’s Zircon hypersonic missiles would help make Russia’s push for security guarantees “more convincing.”

Friday’s launches were the latest in a series of test of Zircon, which Putin said is capable of flying at nine times the speed of sound to a range of more than 1,000 kilometers (620 miles). They marked the first time Zircon missiles were launched in a salvo, indicating the completion of tests before the new missile enters service with the Russian navy next year and arms its cruisers, frigates and submarines.

Peskov on Sunday also pointed at Putin’s earlier warning that a Ukrainian offensive against the rebel-held territories would entail “grave consequences” for Ukraine’s statehood, adding that “they know it well in Kyiv and they know it well in Washington.”

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