France warns Russia of 'massive' consequences if Ukraine threatened

France on Wednesday warned Moscow it would face "strategic and massive consequences" if Russia attacked Ukraine, as concern grows over a new troop build-up on the border.

"Strong messages were sent to Russia that a new attack on the territorial integrity of Ukraine would have strategic and massive consequences," the foreign ministry said in a statement following telephone talks this week between the leaders of France, Germany, Italy, the UK and United States.

It said that the so-called Quint of the five Western allies had in their talks "expressed their determination that the sovereignty of Ukraine be respected."

Russia in 2014 annexed the Ukrainian Black Sea peninsula of Crimea, in a move never recognised by the international community. In the same year, pro-Moscow separatists seized control of two Ukrainian eastern regions, declaring unrecognised breakaway statelets.

The French statement came after 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 spoke via 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.