BRUSSELS — NATO Secretary-General Jens Stoltenberg is concerned about Russia's continued military buildup around Ukraine.
He says Moscow has now deployed more troops and military equipment to neighboring Belarus than at any time in the last 30 years.
More than 100,000 Russian troops are stationed near Ukraine's northern and eastern borders. That raises concern that Moscow might invade again as it did in 2014.
Russian officials deny an invasion is planned.
Stoltenberg said Thursday that the buildup in Belarus is the biggest Russian deployment there since the Cold War and that Russian troop numbers there are likely to climb to 30,000.
Though Russia denies it's planning an invasion of Ukraine, it has laid out a series of demands it says will improve security in Europe. Those demands include a promise that NATO will not extend an invitation to Ukraine and a guarantee that the alliance will remove troops from Eastern Europe.
But the U.S. and the Western alliance have firmly rejected any concessions on Moscow's suggestions. Many of Russia's demands are nonstarters for NATO, creating a stalemate that many fear can only end in a war.
On Wednesday, the Pentagon announced it was sending 3,000 U.S. troops toward Eastern Europe. About 2,000 of those military members will be deployed from Fort Bragg, North Carolina, to Poland and Germany. Another 1,000 troops based in Germany will be sent to Romania.
"The current situation demands that we reinforce Eastern flank," Pentagon spokesperson John Kirby said Wednesday.
In the past, Putin has expressed frustration with the Soviet breakup of some countries, like Belarus and Ukraine. According to an Associated Press analysis, Putin sees those countries as part of a historic Russian linguistic and Orthodox motherland.