The US has told Vladimir Putin to choose between dialogue and confrontation on the eve of a critical week of diplomacy over Ukraine as Russian troops remained massed along its borders.

Senior diplomats from the US and Russia were expected to meet in Geneva on Sunday evening and Monday to discuss Moscow’s demands, set out last month in two draft treaties, one with the US and one with Nato. Much of their content is unacceptable to Washington and the alliance, most importantly a pledge that Ukraine will never be a Nato member.

Russia has 100,000 troops positioned near Ukraine and a similar number are primed to be mobilised at short notice, according to the US secretary of state, Antony Blinken, who said on Sunday that the week’s diplomacy was a moment of truth for the Russian president.

“There are two paths before us,” he told CNN. “There’s a path of dialogue and diplomacy to try to resolve some of these differences and avoid a confrontation. The other path is confrontation and massive consequences for Russia if it renews its aggression on Ukraine. We’re about to test the proposition about which path President Putin’s prepared to take.”

The Biden administration insists that sovereign states’ right to apply for Nato membership is not negotiable. Nor are US troop deployments in Europe, administration officials have stressed. They said, however, that Washington would discuss other security guarantees, such as mutual limits on missile deployments and military exercises on the continent. That would fall far short of the comprehensive changes Moscow is demanding.