The Biden administration is officially welcoming the first group of refugees coming to the U.S. under the “Uniting for Ukraine” program, the Department of Homeland Security announced Monday.

So far, about 6,000 Ukrainians of the 19,000 who applied have received authorization to travel to the U.S. after passing background checks and biometric screenings, DHS said in a statement.

The program requires Ukrainians to have a private sponsor in the U.S. who must also complete a background check and prove they have the financial means to support those granted refuge.

The program is part of President Joe Biden’s promise to allow 100,000 Ukrainians to seek refuge in the U.S. Other legal pathways are also still available through the State Department that will count toward the 100,000 objective.

“We are proud to deliver on President Biden’s commitment to welcome 100,000 Ukrainians and others fleeing Russian aggression to the United States. The Ukrainian people continue to suffer immense tragedy and loss as a result of Putin’s unprovoked and unjustified attack on their country,” Secretary of Homeland Security Alejandro Mayorkas said in a statement last month. “DHS will continue to provide relief to the Ukrainian people, while supporting our European allies who have shouldered so much as the result of Russia’s brutal invasion of Ukraine.”

Before “United for Ukraine” was established, about 20,000 Ukrainians without prior authorization entered the U.S. along the southern border, according to a DHS court filing.

With the pre-authorization program up and running, authorities have taken a harder line on admitting Ukrainians who show up at the border without proper documentation. That shift left dozens stranded on the Mexican side of a border crossing near San Diego and potentially many more elsewhere along the border, the San Diego Union Tribune reported last month.

More than 5.8 million refugees have fled Ukraine, according to the UNHCR, with the majority traveling to eastern European nations including Poland and Romania.