Washington (CNN) The White House is asking Congress for $4.5 billion in emergency funding as it confronts an influx of migrants on the southern border.

The request comes after heated battles over spending on border security, which President Donald Trump has insisted must include money for his long-promised wall.

The $4.5 billion includes : $3.3 billion for humanitarian assistance, $1.1 billion for border operations, and $178 million for mission support, like additional personnel, according to the request sent to lawmakers.

A senior administration official said the funds would not be used for Trump's border wall.

"We can confirm that the funds requested in the supplemental will not be used to build additional miles of wall on the southwest border," the official said.

The official stressed that the request is necessary to address a "dire" situation along the border. Agencies have been strained, in part, by the shift in demographics -- from single adult males to families and children from Central America seeking asylum.

"Agencies are literally running out of funds," the official said.

Facing resistance from Democrats over the billions he requested for the wall, Trump declared a national emergency earlier this year in a bid to secure the funds without lawmakers' approval.

The budget proposal he unveiled this year also allocated billions for border security.

On Tuesday, acting Homeland Security Secretary Kevin McAleenan said a supplemental request was coming that would seek funding for temporary and semi-permanent migrant processing facilities, additional personnel along the border, increased detention capacity and upgrades to "overtaxed" information technology systems.

"Given the scale of what we are facing, we will exhaust our resources before the end of this fiscal year," he told a House appropriations subcommittee.

The request isn't intended to create "policies to be aggressive on immigration," but rather to address the increased flows of migrants, according to a Department of Homeland Security official.

It also includes a request for additional bed space and transportation funding for Immigration and Customs Enforcement. ICE is currently averaging around 50,000 people in custody, which is above the current detention funding levels. A DHS official acknowledged that the request for additional beds is likely to get pushback from lawmakers.

The request is expected to run into problems on Capitol Hill because of serious Democratic concerns over intent on immigration broadly, as well as the still-languishing disaster relief supplemental, which has imploded the last few weeks.