US Vice President Kamala Harris and Romania’s president will on Friday meet to discuss growing concerns about the influx of displaced people fleeing Ukraine for Romania and elsewhere in eastern Europe due to Russia’s invasion.

It’s a problem that Biden administration officials and European leaders warn will likely get more complicated in the days and weeks ahead.

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Harris’ talks in Bucharest with President Klaus Iohannis come after she spent Thursday in Poland, which has already welcomed some 1.5 million Ukrainians since the invasion began. She met in Warsaw with Polish President Andrzej Duda and Prime Minister Mateusz Morawiecki, Ukrainian refugees, and others in hopes of getting a fuller picture of the unfolding humanitarian crisis.

The southeastern European country of Romania — a nation of about 19 million — had taken in more than 84,000 displaced people as of Tuesday, according to United Nations data. Other countries on NATO’s eastern flank, including Hungary, Moldova and Slovakia, have also welcomed tens of thousands of refugees.

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Harris said the US was “absolutely prepared” to support those “who understand the moral obligation we should feel to help people who are fleeing harm and seeking refuge; the burden we should all be prepared to take on to support those people who are fleeing their home when they don’t want to leave.”

Duda, in a press conference with Harris, said Polish leaders are “aware that the problem is growing and that this problem is increasing.”

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“We have to somehow handle it, and we do not have the experience,” he said.

Overall, more than 2.3 million people have fled Ukraine since the start of the war, and the number of displaced people continues to grow daily. The United Nations warns that up to 5 million people could flee Ukraine. That would make it the biggest humanitarian crisis in Europe since World War II.

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Duda said he had asked Harris to relay to President Joe Biden that Poland would like to see expedited visa procedures for Ukrainians who have family living in the United States so that they could resettle in the US at least temporarily.

Harris said most refugees who have fled Ukraine prefer to remain in Europe. Earlier this month, the administration offered humanitarian relief to Ukrainians in the United States, which could protect thousands from being deported to their war-torn homeland. Ukrainians already in the US would be able to stay in the US for up to 18 months under the federal program known as Temporary Protected Status.

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The Pentagon announced last month it was deploying a Stryker squadron of about 1,000 additional soldiers to Romania, a NATO member, as the Biden administration looks to bolster the military alliance’s presence on NATO’s eastern flank.

US officials remain concerned about Romania’s vulnerability in the midst of Russian activity in the Black Sea.

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Before departing Warsaw for Romania on Friday, Harris met with US and Polish troops.