Biden arrived in Warsaw late on Monday after a dramatic visit to Kyiv where he met President Volodymyr Zelenskiy, who is seeking more weaponry as Ukraine gears up for a spring offensive against the Russians.

Biden will give a speech rallying support for Ukraine as the war enters its second year on Feb. 24 with no end in sight.

He was due to meet Polish President Andrzej Duda to discuss collective support for Ukraine and thank Warsaw for helping the United States and other countries to deliver military and humanitarian aid.

Poland has NATO's longest border with Ukraine and has been the main route in for weapons and out for refugees. Duda's foreign policy adviser said the men would also discuss Poland's security, and scaling up NATO resources there.

"It is no secret that we will talk about increasing the presence, also in terms of infrastructure, of NATO," Marcin Przydacz told private broadcaster TVN 24.

The visit was welcomed by ordinary Poles and by the 2.5 million Ukrainians, mostly women and children refugees from the conflict, now living in the country.

"We hope that they (the U.S.) will increase shipments of arms, that things at the front will improve and that we will win," said Alina Kiiko, 32, a Ukrainian in central Warsaw.

On the Roman Dmowski roundabout in the centre of city, a giant advertising screen ran the slogan: "Biden, give F-16 to Ukraine" in English, referring to U.S. fighter jets.

Warsaw resident Marian Switala, 70, said he hoped "that this conflict will somehow be resolved and there will be peace in Ukraine and the surrounding area".

EASTERN FLANK

Before returning to Washington on Wednesday, Biden will meet leaders of the Bucharest Nine, the countries on NATO's eastern flank, to reaffirm support for their security.

While Biden was in Kyiv on Monday, the State Department announced more support for Ukraine comprising $450 million of artillery ammunition, anti-armour systems and air defence radars, and $10 million for energy infrastructure.

Biden has not, however, approved Ukraine's request for fighter jets.

Lithuanian President Gitanas Nauseda's message to Biden will be that it wants "greater involvement of the U.S. in Europe, NATO's eastern flank and, of course, more aid to Ukraine," his chief foreign policy adviser told Lithuanian radio on Tuesday.

"Lithuania and other like-minded countries have several requests, which concern air defence, forward defence presence, air defence systems, and greater investments in the defence industry," Asta Skaisgiryte said.

Later this week, Washington will announce additional sanctions against individuals and companies that are "trying to evade sanctions and backfill Russia's war machine," a White House spokesperson said.

Biden arrives in Poland on the day of a major address from Russian President Vladimir Putin, who condemned the West.

A year ago, Biden warned sceptical allies that a massive buildup of Russian troops along Ukraine's borders was the precursor to war. At the time, even some inside his own government questioned Ukraine's ability to withstand an invasion.

Instead, Ukraine's forces held Kyiv and drove Russia back out of some of the territory it seized in the early weeks of the war, helped by Western weapons, ammunition and equipment.

The United States has sent more than $24 billion in security assistance, but U.S. officials say the war may continue for many months or even years.

(Reporting by Steve Holland in Washington, Alan Charlish, Pawel Florkiewicz, Anna Koper and Andrius Sytas in Warsaw; writing by Steve Holland, Niklas Pollard and Gwladys Fouche; editing by Ross Colvin, Sandra Maler, Kevin Liffey, Peter Graff)

By Nandita Bose and Alan Charlish