US President Joe Biden warned President Vladimir Putin on Tuesday of “strong” Western economic blowback against any Russian attack on Ukraine, while the Kremlin leader demanded guarantees that the NATO alliance keep clear of Russia.

The two leaders met by video link in a two-hour summit seen as a vital chance to defuse tension on the Russian-Ukrainian frontier, where Russia has deployed up to 100,000 troops, sparking fears of a major war in Europe.

Russia denies planning to invade Ukraine, where it already seized swaths of territory in 2014. However, Biden made clear that economic pain, perhaps including “risk” to Russia’s new Nord Stream 2 natural gas pipeline supplying Europe, would follow if it does.