On the second day of his trip to Poland, US President Joe Biden is expected to deliver a major address rallying resistance to Russia's war in Ukraine.

US President Joe Biden is in Warsaw on Saturday for meetings with Polish and Ukrainian government officials, followed by an address underlining the global response to Russia's war in Ukraine.

The White House has said Biden's address will "deliver remarks on the united efforts of the free world to support the people of Ukraine, hold Russia accountable for its brutal war, and defend a future that is rooted in democratic principles.''

According to the US Embassy in the Polish capital, Biden will deliver his address at Warsaw's Royal Castle between 5 and 6 p.m. local time (1600 and 1700 UTC).

Poland wants US security guarantees

Biden is due to meet with Polish President Andrzej Duda for closed-door talks at the presidential palace.

The two leaders are expected to speak about security guarantees, and the controversy over an offer by Poland to arm Ukraine with warplanes via a US air base that was turned down by Washington.

Also on Saturday's agenda, the White House said Biden would "drop by" a meeting between US Secretary of State Antony Blinken and US Defense Secretary Lloyd Austin with Ukrainian Foreign Minister Dmytro Kuleba and Defense Minister Oleksii Reznikov in Warsaw.

As the largest NATO member in the former eastern bloc, Poland is playing an important role in the Western response to Russia's war in neighboring Ukraine.

Pawel Soloch, the head of Poland's National Security Bureau, said Friday that Warsaw wants an "unshakable guarantee" that the US would defend Poland in the event of an attack.

Biden to visit refugee center in Warsaw

The US president is also expected to accompany Polish Prime Minister Mateusz Morawiecki and Warsaw Mayor Rafal Trzaskowski to Warsaw's National Stadium, where Ukrainian refugees are being registered and provided with aid.

Poland has taken in more than 2.2 million out an of an estimated 3.5 million refugees who have fled Ukraine since the Russian invasion began more than a month ago.

After arriving in Poland on Friday, Biden visited a refugee center near the southeastern city of Rzeszow, about 70 kilometers (45 miles) from the Ukrainian border.

Biden's visit to Poland follows his appearance at a trio of summits in Brussels on Thursday.