Trump administration requests $4.5 billion in new border funding

The proposal is in addition to the annual budget.

The Trump administration is requesting an additional $4.5 billion in emergency spending to address the "humanitarian and security crisis" at the southern border, senior administration officials said on a call with reporters on Wednesday afternoon.

Tens of thousands of migrants are arriving at the southern border each month with record numbers of families and children attempting to cross. U.S. officials said more than 100,000 people arrived in March and that the numbers are on track to reach 1 million by September.

Included in the proposal is $3.3 billion in "humanitarian assistance" for new detention facilities and shelters for families, as well as clothing, diapers and baby formula.

Another $1.1 billion will be used for border operations and $178 million will be used for mission support personnel, administration officials said.

Democrats on the House funding committee took issue with the administration's attempts to expand enforcement measures.

"Through its callous immigration policies, the Trump administration has contributed to a humanitarian emergency on the border," House Appropriations Committee Chairwoman Nita Lowey said in a statement. "As a country, we must do more to meet the needs of migrants -- especially children and families -- who are arriving in increasing numbers."

The proposal represents a massive increase compared to the $800 million in humanitarian aid that the administration requested during the budget fight earlier this year.

At the time, the White House billed it as a significant offer to secure border wall funding from Democrats. The money in the latest request will not be used to build President Donald Trump's border wall. Those barriers are being funded, in part, by the national emergency the president declared in February.

The U.S. Department of Health and Human Services, which cares for some 12,000 unaccompanied migrant children in shelters scattered across the U.S., says that without the $2.8 billion needed for bed space, the agency could run out of money in June.

"Without additional funds, HHS may be forced to scale back services, may be unable to handle further growth in the number of children in care, and may have to reallocate more funds from refugees and victims of trafficking and torture," according to an HHS statement.

Acting Homeland Security Secretary Kevin McAleenan testified this week that his agency was running out of money and would rely on these supplemental funds as it continues to grapple with a record influx of migrants at the southern border. Nearly 40,000 children crossed the border in April alone, the acting chief told Congress Tuesday.

"Given the scale of what we're facing, we'll exhaust our resources before the end of this fiscal year," McAleenan said Tuesday.

ABC's Rachel Scott and Anne Flaherty contributed to this report.