"It is no secret that we will talk about increasing the presence, also in terms of infrastructure, of NATO"

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 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.

Duda's foreign policy adviser said the men would also discuss Poland's security and scaling up the resources of the transatlantic military alliance 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 TVN24.

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

"President Biden will make it clear that the United States will continue to stand with Ukraine, as you've heard him say many times, for as long as it takes," said John Kirby, the White House national security spokesperson.

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-armor systems and air defense radars, and $10 million for energy infrastructure.

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

Later this week, the United States 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 visited Kyiv the day before a major address from Russian President Vladimir Putin, likely to set out aims for the second year of what he now calls a proxy war against the armed might of Washington and NATO.

A year ago, Biden warned skeptical 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, predicting that the capital would quickly fall.

Instead, Ukrainian fighters held Kyiv and have driven Russia back out of some of the territory it seized in the early weeks of the war, helped by large quantities of 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.