Former Soviet leader Mikhail Gorbachev warned Friday that "it all looks as if the world is preparing for war."
Gorbachev, who was head of the socialist state when it dissolved in 1991, wrote the comments in an opinion piece for Time magazine.
"More troops, tanks and armored personnel carriers are being brought to Europe," the 85-year-old wrote. "NATO and Russian forces and weapons that used to be deployed at a distance are now placed closer to each other, as if to shoot point-blank."
The 1990 Nobel Peace Prize-winner added: "Politicians and military leaders sound increasingly belligerent and defense doctrines more dangerous. Commentators and TV personalities are joining the bellicose chorus. It all looks as if the world is preparing for war."
Thousands of U.S. troops have been sent to eastern Europe in recent weeks, the largest deployment of its kind since the Cold War.
Gorbachev oversaw an agreement with the U.S. to reduce their nuclear arsenals. President Donald Trump, however, has suggested he could bolster the number of such weapons at his disposal, something that would reverse decades of American policy.
Trump has said he would like to expand America's nuclear weapons, telling MSNBC's Morning Joe in December: "Let it be an arms race."
This proposed reversal of decades of U.S. policy was in part what moved a group of scientists Thursday to move the metaphorical Doomsday Clock to two minutes and 30 seconds before midnight — the time that represents when a catastrophic nuclear event can annihilate the earth.
Trump has signaled he may seek a rapprochement with his Russian counterpart, Vladimir Putin, including lifting sanctions imposed by Barack Obama over Moscow's annexation of Crimea.
Trump has also called NATO "obsolete", and Russian media said he and Putin were expected to speak on the phone Saturday.
Some expects fear that if Trump undermines NATO and cozies up to Russia, Putin may be emboldened to interfere in other former Soviet countries.
"While state budgets are struggling to fund people's essential social needs, military spending is growing," Gorbachev wrote. "Money is easily found for sophisticated weapons whose destructive power is comparable to that of the weapons of mass destruction; for submarines whose single salvo is capable of devastating half a continent; for missile defense systems that undermine strategic stability."
Gorbachev urged the United Nations Security Council to adopt a resolution stating that "nuclear war is unacceptable and must never be fought," and said the initiative to sign it should come from Trump and Putin.