Senate Democrats are demanding the administration brief them on how it will implement more than $4.5 billion in recently passed funding tied to the U.S.-Mexico border.

Roughly two dozen Democrats sent a letter to President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE warning that it would be "unacceptable" for the administration to redirect the money toward unintended areas or refuse to spend the new funding, the majority of which is directed toward humanitarian aid.

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"Congress intends to scrutinize the expenditure of these funds and will use all methods of oversight to ensure that the requirements of the law are faithfully executed," they added.

The Democratic senators are requesting the Departments of Defense, Health and Human Services, Justice and Homeland Security provide them a briefing by July 22 to explain how they'll implement the border supplemental bill.

In addition to a briefing, Democrats have specific asks for each of the departments, including wanting a plan from HHS on how they plan to increase staff for and services offered by the Office of Refugee Resettlement, a schedule from DHS for constructing new shelters and migrant processing facilities and an estimate from the Pentagon on how much it will cost to pay for activity-duty and National Guard deployments along the border.

Congress passed the border supplemental bill in late June after months of wrangling with the administration.

Acting Homeland Security Secretary Kevin McAleenan sent a letter this week to Speaker Nancy Pelosi Nancy PelosiPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline Trump signs largely symbolic pre-existing conditions order amid lawsuit MORE (D-Calif.) saying the funding had already helped improve conditions for migrants and agents along the border.

"The supplemental funding provided by Congress meets immediate acute needs at the border and has already improved conditions for children," wrote McAleenan in the letter dated Wednesday but released Friday by DHS.

The letter from Senate Democrats comes as Senate Minority Leader Charles Schumer Chuck SchumerPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' 3 reasons why Biden is misreading the politics of court packing Cruz blocks amended resolution honoring Ginsburg over language about her dying wish MORE (D-N.Y.) is leading a delegation from the caucus to migrant detention facilities along the U.S.-Mexico border. McAleenan is joining them on the trip.

Conditions at migrant facilities along the border have jumped into the national spotlight after the Department of Homeland Security's inspector general released a report earlier this month that found "dangerous overcrowding" and "prolonged detention of children and adults" at facilities in the Rio Grande Valley.