Joe Biden has added a stop in Poland to his trip this week to Europe for urgent talks with NATO and European allies, as Russian forces concentrate their fire upon cities and trapped civilians in a nearly month-old invasion of Ukraine.

Biden will first travel to Brussels and then to Poland on Friday to meet with leaders there, press secretary Jen Psaki said in a statement Sunday night.

Poland is a crucial ally in the Ukraine crisis. It is hosting thousands of American troops and is taking in more people fleeing the war in Ukraine — more than two million — than any other nation in the midst of the largest European refugee crisis in decades.

Biden will travel on Friday to Warsaw for a bilateral meeting with President Andrzej Duda. Biden will discuss how the U.S., along with its allies and partners, is responding to “the humanitarian and human rights crisis that Russia’s unjustified and unprovoked war on Ukraine has created,” Psaki said.

White House officials have said Biden has no plans to travel to Ukraine. Secretary of State Antony Blinken, while in Poland this month, briefly crossed into neighboring Ukraine in a show of solidarity alongside that country’s foreign minister, Dmytro Kuleba. Poland has been one of the most vocal countries in asking fellow NATO members to consider getting more involved to rein in the bloodshed.

Russian President Vladimir Putin’s invasion of Ukraine largely has united the U.S. and NATO and European allies, as well as allies in Asia and elsewhere. The United States and European governments see Moscow’s military aggression as a threat to their security and strategic interests.

Biden and NATO have said repeatedly that while the U.S. and NATO will provide weapons and other defensive support to non-NATO member Ukraine, they are determined to avoid any escalation on behalf of Kyiv that risks a broader war with Russia.

The Pentagon on March 9 rejected a Polish proposal for providing Ukraine with MiG fighter jets via a NATO air base, saying allied efforts against the Russian invasion should focus on more useful weaponry and that the MiG transfer with a U.S. and NATO connection would run a “high risk” of escalating the war.

Ukraine’s president, Volodymyr Zelenskyy, has pleaded for the U.S. to provide his military with more aircraft and advanced air-defense systems. NATO and the United States have rejected his appeals to establish a “no-fly zone” over Ukraine to suppress Russian air power, saying it would put Western forces in direct conflict with Russian ones.

Determined resistance by Ukrainian fighters when Russian tanks and troops rolled into Ukraine in late February quickly defeated Russian forces’ attempts to storm Ukraine’s capital and unseat the westward-looking government. Denied an easy and early victory, Russia’s military is reverting to the scorched earth tactics of its past offensives in Syria and Chechnya, and pounding population centers with airstrikes and artillery barrages that leave civilians like those in the port city of Mariupol able to safely venture out for food or water, to bury the dead, or to flee.