President Joe Biden said a Russian invasion of Ukraine remains “very high,” and that he expects Russian President Vladimir Putin to order an attack within days.

“Every indication we have is they’re prepared to go into Ukraine,” Biden said Thursday morning to White House reporters.

He said evidence suggests Russia is “engaged in a false flag operation to have an excuse to go in,” but added that a diplomatic solution is still possible. “There is a path. There is a way through this,” Biden said.

But that path is complicated by a surprising development in Moscow; the Russian government ordered the deputy chief of mission at the U.S. Embassy in Moscow, Bart Gorman, to leave the country last week. The U.S. State Department called the unexplained move – which was first revealed Thursday – “an escalatory step.”

Meanwhile, Secretary of State Antony Blinken appeared at the United Nations on Thursday and said there’s no reason to believe Russian claims that it has been removing troops from its border with Ukraine.

“Russia says it’s drawing down those forces,” he said. “We do not see that happening on the ground. Our information indicates clearly that these forces, including ground troops, aircraft, ships, are preparing to launch an attack against Ukraine in the coming days,” Blinken said.

Blinken echoed Biden’s warning that a false flag operation was possible, including a “fabricated, so-called terrorist bombing inside Russia” or the “invented discovery of a mass grave.”

Blinken made a thinly-veiled allusion to the U.N. speech delivered by then Secretary of State Colin Powell in the run-up to the Iraq war. Powell insisted the country had weapons of mass destruction. It didn’t.

“I’m mindful that some have called into question our information, recalling previous instances where intelligence did not ultimately bear out,” Blinken said. “But let me be clear: I am here today not to start a war, but to prevent one.”

As diplomats and world leaders issued their warnings, violence began to expand in Ukraine. The Wall Street Journal reports:

Violence escalated in eastern Ukraine on Thursday, with Russian-backed separatists and authorities in Kyiv trading accusations over cease-fire violations along the front line separating the two sides as Western governments said Moscow continued to mass troops on the borders of its smaller neighbor.

A kindergarten and a school in Ukrainian-held towns were hit by mortar shells, according to the Ukrainian army and local residents. Authorities in separatist areas said mortar attacks had also damaged several buildings in towns there. No fatalities were reported on either side.

Ukrainian President Volodymyr Zelensky, who was visiting front-line troops, described the damage to the schools as a “big provocation” by pro-Russian forces.

Russia blamed the outbreak on Ukraine.

“Reports of alleged abnormal military activity by Ukraine in Donbas are a blatant attempt by the Russian government to fabricate pretexts for invasion,” U.K. Foreign Secretary Liz Truss said in a tweet. “This is straight out of the Kremlin playbook.”