MOSCOW — The Kremlin said Friday that President Vladimir Putin will seek binding guarantees precluding NATO’s expansion to Ukraine during a planned call with US President Joe Biden, while the Ukrainian defense minister warned that Russia could invade his country next month.

Tensions between Russia and the West have escalated in recent weeks, with Ukraine, the U.S. and other Western allies increasingly concerned that a Russian troop buildup near the Ukrainian border could signal Moscow’s intention to invade. The U.S. has threatened the Kremlin with the toughest sanctions yet if it launches an attack, while Russia has warned that any presence of NATO troops and weapons on Ukrainian soil would cross a “red line.”

Ukrainian Defense Minister Oleksii Reznikov told lawmakers Friday that the number of Russian troops near Ukraine and in Russian-annexed Crimea is estimated at 94,300, warning that a “large-scale escalation” is possible in January.

Amid the mounting tensions, Putin’s foreign affairs adviser Yuri Ushakov told reporters Friday that arrangements have been made for a Putin-Biden call in the coming days, adding that the date will be announced after Moscow and Washington finalize details.

On Thursday, U.S. Secretary of State Antony Blinken met face-to-face with his Russian counterpart Sergey Lavrov in Stockholm to demand that Russia pulls back troops from the border with Ukraine. Lavrov retorted that the West was “playing with fire” by denying Russia a say in any further NATO expansion into countries of the former Soviet Union.

Ukraine has pushed to join the alliance, which holds out the promise of membership but hasn’t set a a timeline.

Ushakov noted that during the call with Biden Putin will raise his demand for a document that would exclude any NATO moves further east. Russia wants a legally-binding agreement that would “exclude any further NATO’s expansion eastward and the deployment of weapons systems that would threaten us on the territories of neighboring countries, including Ukraine,” he said.

The Kremlin aide said that Russia long has pushed for such arrangements, emphasizing that they have become particularly acute amid the latest buildup of tension, adding that “it simply can’t continue like that.”

He charged that in the early 1990s the Soviet and Russian leadership received verbal assurances from Western leaders that NATO wouldn’t expand eastward, but the West reneged on those promises in the following years that saw former Soviet bloc countries and ex-Soviet republics join the alliance.

Russia and Ukraine have remained locked in a tense tug-of-war after Russia annexed Ukraine’s Crimean Peninsula in 2014 and threw its weight behind a separatist insurgency in Ukraine’s eastern industrial heartland, known as the Donbas. More than 14,000 people have died in the fighting.

Ukraine’s defense minister warned Friday that an escalation “is a probable scenario, but not certain, and our task is to avert it.”

“Our intelligence service analyzes all scenarios, including the worst ones,” Reznikov said. “The most probable time when (Russia) will be ready for the escalation is end of January.”

Konstantin Kosachev, a deputy speaker of the upper house of parliament, reaffirmed Moscow’s denial that it was pondering an attack.

“We don’t have any plans to attack Ukraine. We don’t have any heightened military activity near Ukraine’s borders. There is no preparation underway for an offensive,” Kosachev told Russia’s state TV channel Russia-24.

The Kremlin has voiced concern that Ukraine may use force to reclaim control of the rebel east. And adding to the tensions, the head of a Russian-backed, self-proclaimed separatist republic in eastern Ukraine said Thursday that he could turn to Moscow for military assistance if the region faced a Ukrainian attack.

Reznikov said Ukraine wouldn’t do anything to provoke Russia but is prepared to respond in case of an attack. “Ukraine is most interested in political and diplomatic resolution,” the defense minister said.