The Biden administration is expected to announce new details soon about how it will offer Ukrainian refugees to enter the United States on humanitarian grounds, according to a source familiar with the planning.

The move comes nearly a month after President Joe Biden pledged as many as 100,000 Ukrainians would flee the invasion.

More than 5,000 Ukrainians attempted to enter the United States in March, including 3,274 at the southern border with Mexico, according to US Customs and Border Protection data.

The humanitarian parole program, which falls under the Department of Homeland Security and could be announced as soon as Thursday, will require Ukrainians wishing to enter the United States to be sponsored by a U.S. citizen or individual, including resettlement and nonprofit organizations, he said. Source.

To be eligible, the source said people will have to undergo rigorous security checks – including CV and biometrics checks, full vaccinations and other public health requirements, such as receiving a Covid-19 vaccine.

Backers will have to pass their own security checks and declare their financial support.

Through this process, the source said, Ukrainian applicants can travel to the United States and be considered for a parole order on humanitarian grounds, on a case-by-case basis, for up to two years. If accepted, individuals will be eligible for a work permit.

According to the source, the Biden administration may start receiving applications for the program as soon as the end of April.

In addition to the humanitarian parole program, the State Department is working to expand European Refugee Admissions Program operations, the source added, with the goal of providing eligible individuals with better access to the Luttenberg program. A 1989 initiative aimed at helping religious people fleeing persecution in the Soviet Union – as well as ramping up referral mechanisms for Ukrainians seeking permanent resettlement.

White House Press Secretary Jen Psaki told reporters Wednesday that the administration is finalizing details on how to host up to 100,000 Ukrainian refugees in the United States.

A White House spokesperson declined to comment on the new details, but said additional details about the administration’s efforts would be announced “soon.” The Department of Homeland Security did not immediately respond to a request for comment.

More than five million people have fled Ukraine since the start of the Russian invasion in late February, the United Nations High Commissioner for Refugees said on Wednesday.