NATO said Monday that it is putting forces on standby as member states bolster the alliance’s “deterrence” presence in Eastern Europe. The military alliance is warily watching Russia’s massive troop buildup along its border with Ukraine, which is not a NATO member but has aspirations to join. Denmark is sending a frigate and F-16 fighter jets to Lithuania while Spain is sending warships to Bulgaria, with fighter jets and French troops on standby. Russia insists it has no plans to invade Ukraine.

“NATO will take all necessary measures to protect and defend all allies, including by reinforcing the eastern part of the alliance,” Secretary-General Jens Stoltenberg said Monday. “We will always respond to any deterioration of our security environment, including through strengthening our collective defense.” NATO members Lithuania, Latvia, and Estonia confirmed over the weekend that they are sending U.S.-made anti-tank and anti-aircraft missiles to Ukraine, with the U.S.’s approval. 

Britain on Monday joined the U.S. in bringing home staff at its embassy in Kyiv, Ukraine’s capital, citing the “growing threat from Russia” but describing the diplomatic drawdown as precautionary. European Union foreign policy chief Josep Borrell said the EU won’t join the U.S. and Britain yet, so as not to “dramatize” the situation, but the EU is monitoring the situation. 

Ukraine’s foreign ministry criticized the U.S.’s withdrawal of some embassy personnel and their families as “premature and a manifestation of excessive caution” that plays into Russia’s hands. “In fact, there have been no cardinal changes in the security situation recently: the threat of new waves of Russian aggression has remained constant since 2014 and the buildup of Russian troops near the state border began in April last year,” foreign ministry spokesman Oleg Nikolenko said in a statement.

The EU foreign ministers are meeting Monday to present a united front in support of Ukraine, with serious economic consequences for Russia if it invades. Irish Foreign Minister Simon Coveney also said Monday that Ireland objects to Russia’s plans to hold military exercises 150 miles off Ireland’s coast, inside Ireland’s exclusive economic zone but international waters. “This isn’t a time to increase military activity and tension in the context of what’s happening with and in Ukraine,” he said.