"The increased (US) military presence in Poland in coordination with NATO... demonstrates NATO's vitality," Poland's President Andrzej Duda said at a press conference in Vilnius with his Lithuanian counterpart Gitanas Nauseda.

US President Donald Trump in September expanded US rotations in Poland by 1,000 troops, up from 4,500, but said it did not reflect any increased threat from Russia.

"Like President (Gitanas) Nauseda, I absolutely can't see that NATO has any trouble with its vitality," Duda added.

For his part, Nauseda warned that NATO's 29 members "should not raise the slightest doubt that this organisation (NATO) remains our essential security guarantor."

In October Washington also began deploying a battalion of troops and dozens of tanks to Lithuania for an unprecedented six-month rotation in addition to an existing NATO deployment there designed to deter neighbouring Russia.

Two years ago, NATO deployed four multinational battalions of around 1,000 troops each to Poland and Baltic states Estonia, Latvia and Lithuania as tripwires against possible Russian adventurism in the region after Moscow's 2014 annexation of Crimea from Ukraine.

The four countries, dominated by the Soviet Union for more than 40 years after World War II, had lobbied hard for the NATO deployments as an extra security buffer.

French President Emmanuel Macron stirred controversy earlier this month saying that he believed NATO was undergoing "brain death," lamenting a lack of coordination between Europe and the United States in an interview with The Economist magazine.

Macron's controversial remarks came ahead of NATO's December 4 summit in Britain.