MOSCOW (TNS) — Russian President Vladimir Putin on Tuesday accused the United States of an “aggressive” approach regarding Ukraine, as NATO partners debated how to respond to Moscow’s build-up of troops on the Ukrainian border.

“In case of continuation of the rather aggressive line of our Western colleagues, we will respond with adequate military-technical measures, will react harshly to the unfriendly steps,” Putin said at a Defense Ministry meeting in Moscow on Tuesday. 

He again pushed for NATO and the United States to provide Russia with legally binding security guarantees. In concrete terms, Putin is calling on NATO to renounce further eastward enlargement, including the admission of Ukraine as a member. 

Putin made it clear that Russia sees its security threatened by NATO’s advance. However, Putin stressed that this was “not an ultimatum,” but an offer for dialogue. 

In Ukraine, on the other hand, President Volodymyr Zelenskyy reiterated the demand for his country’s rapid NATO accession in view of the tensions with Russia. 

“We want a very clear time perspective from NATO. A very concrete one. And we want to get it in 2022,” he said during a speech to all Ukrainian ambassadors on Tuesday. 

Likewise, he said, EU membership should be achieved in the next few years. Both have been enshrined as goals in the Ukrainian constitution since 2019.

Russian Defense Minister Sergei Shoigu criticized the growing militarization of Ukraine and an increase in maneuvers on Russia’s borders at the meeting with Putin. 

Russian Foreign Minister Sergei Lavrov made comments at a press conference, warning the US and the West as a whole not to cross “red lines.” NATO should not move any closer to Russia’s borders. 

Putin accused the US of bearing responsibility for the current tensions in Europe. “They do what they want,” the Russian leader said, referring to US activities in Ukraine. “After all, this is on the threshold of our house. They should understand that we simply have nowhere to retreat to.” 

For their part, the U.S. and NATO accuse Russia of having deployed tens of thousands of troops near the border with Ukraine.

NATO Secretary General Jens Stoltenberg said on Tuesday that Russia was continuing the “groundless and unexplained” buildup of troops despite international calls to de-escalate. 

Citing NATO intelligence sources, Stoltenberg said Russia was bringing “more and more forces — artillery, combat troops, battle tanks — close to Ukraine’s borders.” 

He added that Moscow’s aggressive rhetoric surrounding the dispute had not stopped.

Despite those concerns, Bulgarian Defense Minister Stefan Yanev said his country would not currently allow NATO troops to be stationed on its soil.