The White House is in early discussions about Biden's travel to Europe

The trip comes on the heels of visits by several top aides, including Vice President Kamala Harris and Secretary of State Anthony Blinken. The White House is exploring a potential stop in Poland as well as elsewhere in Europe, according to a person familiar with the planning.

The trip has not been completed or announced. If the trip does happen, it will be one of the most closely watched visits to Europe by a US president in decades. NBC News was the first to report On discussions of a potential flight.

Russia expanded its offensive into western Ukraine on Sunday, firing missiles near the city of Lviv, hitting a large military base near the Polish border and reportedly killing dozens of people. Poland is a NATO ally, and the military base has conducted joint exercises with NATO and Western military personnel.

Harris visited Poland last week and sought to strengthen Western unity in the face of Russian aggression. The trip marked the second time in a month that Harris has been sent to Europe as the Biden administration seeks to rally international support behind its efforts to punish Russia for its war on Ukraine.

The vice president was tasked with settling the apparent dispute between the United States and Poland over the supply of combat aircraft to Ukraine. Ukrainian President Volodymyr Zelensky was demanding more planes amid the invasion, and Poland surprised the United States with a proposal to supply the nation with its Soviet-era fighter jets. The Pentagon rejected Poland’s plan.

After meeting with the Polish president, Harris said at a press conference alongside the foreign leader that the two countries “are united in what we have done and are ready to help Ukraine and the people of Ukraine.”

As fighting in Ukraine intensifies and the invasion enters its third week, civilians are caught in the crossfire. There were violent explosions in the Ukrainian capital, Kyiv, and authorities reported that at least one person was killed and several people were injured after an apartment building in a Kyiv suburb was bombed on Monday.

More than 2.5 million Ukrainian refugees have been forced to flee in the past two weeks amid the Russian invasion, according to the United Nations.

Zelensky pressed Biden during his last phone call to impose more sanctions to increase pressure on Russia, CNN reported earlier on Monday. The Ukrainian president asked Biden to intensify efforts to cut Russia off from international trade and continue targeting the Russian elite.

Zelensky Scheduled to deliver a default address before Congress on Wednesday. The Ukrainian leader is expected to renew his calls for the United States to send more aid to his country, and also called on the United States and NATO to help establish a no-fly zone over Ukraine. Foreign Minister Anthony Blinken and NATO Secretary General Jens Stoltenberg said such a move was not realistic and could lead to a direct conflict between Russia and NATO.

The United States and its allies have issued a wide range of measures in recent weeks aimed at punishing Moscow for the invasion, including harsh new sanctions and export controls aimed at imposing heavy costs on the Russian economy.

Biden on Friday He called for the suspension of normal trade relations With Russia the United States and its allies are looking to ramp up economic pressure on Russia in response to the nation’s unprovoked attack on Ukraine. The president said the G7 leaders would also seek to deny Russia the ability to borrow from the International Monetary Fund and the World Bank.

This story has been updated with additional information.