Joe Biden's plane landed in Rzeszow, Poland on Friday, as the U.S. president plans to discuss bolstering NATO's eastern flank and see international efforts to provide assistance to millions of Ukrainian refugees who fled their country due to the Russian invasion.
While at Rzeszow-Jasionka Airport, Biden was to receive a briefing on the humanitarian response to help civilians sheltering from Russian attacks inside Ukraine and to respond to the growing flow of refugees fleeing Ukraine.
His schedule was delayed after the plane carrying Polish President Andrzej Duda was turned back on route to Rzeszow and made an emergency landing in Warsaw. Duda later boarded a different aircraft and headed back to eastern Poland. An official in his office said Duda had not been in any danger.
Biden told reporters in Brussels on Thursday that his visit will "reinforce my commitment to have the United States make sure we are a major piece of dealing with the relocation of all those folks, as well as humanitarian assistance needed both inside Ukraine and outside Ukraine."
After the briefing, Biden was to meet with soldiers from the U.S. Army's 82nd Airborne Division stationed there as part of NATO's protection of the alliance's eastern flank.
In the evening, Biden was to travel to the capital Warsaw for talks with Duda. On Saturday, he was scheduled to give what the White House described as a major address.
Poland hopes that Biden's visit will underline the security assurances already made by the United States that it will defend "every inch" of NATO territory. Warsaw is keen to see even more U.S. troops stationed on NATO's eastern flank.
Poland is also likely to raise the idea of an international peacekeeping mission involving troops being stationed in Ukraine, an idea first proposed by ruling party leader Jaroslaw Kaczynski during a trip to Kyiv.
En route to Poland on Air Force One, National Security Adviser Jake Sullivan briefed reporters. Asked whether Russia would try to bomb convoys carrying supplies to Ukraine over land through NATO countries, Sullivan said: "We are doing contingency planning for the possibility that Russia chooses to strike NATO territory in that context or in any other context.
"And the president has been about as clear as one can be about his absolute determination to respond decisively, alongside the other members of our alliance if Russia attacks NATO," Sullivan said.
He also suggested the U.S. and its allies could still impose new measures to punish Russia for its invasion of Ukraine.
"Of course, there are additional measures to tighten the screws on sanctions, and we will be constantly reviewing those," he said.
Moscow calls its actions in Ukraine a "special military operation" to disarm its neighbor. Kyiv and its Western allies call it an unprovoked war of aggression and say Russia's true aim was to overthrow the government of what President Vladimir Putin regards as an illegitimate state.