Alan Gomez

USA TODAY

As thousands of children continue streaming across the nation's southwest border,President Obama asked Congress on Tuesday for $3.7 billion to improve security along the border, provide better housing for the children while they're in custody and to speed up their deportation proceedings.

The White House also wants to increase assistance to El Salvador, Guatemala and Honduras, where most of the children are coming from, to help them stop the rush of people leaving there and to improve their ability to receive the expected influx of deported children.

The request, which has been developed in recent weeks as multiple federal agencies have responded to the surge of children caught crossing the border without their parents, will get its first hearing Thursday before the Senate Appropriations Committee.

Republicans in Congress responded cautiously to Obama's request.

Michael Steel, spokesman for House Speaker John Boehner, R-Ohio, said the Appropriations Committee and other members, including the House working group on the border crisis, will review the White House proposal. "The speaker still supports deploying the National Guard to provide humanitarian support in the affected areas — which this proposal does not address," Steel said.

Senate Minority Leader Sen. Mitch McConnell, R-Ky., called the request a "huge number" and said Congress must closely examine it to see if it's an "appropriate response." Even some Democrats were guarded about the total figure. Senate Majority Leader Sen. Harry Reid, D-Nev., said lawmakers need to be thoughtful about the request. "How we get there, we really don't know," he said.

House Minority Leader Rep. Nancy Pelosi, D-Calif., provided the clearest support for Obama's plan.

"The additional funds are essential to ensure the safety, security, and proper care of the children fleeing violence in their home countries," she said. "Our border security agencies are doing their best to stretch limited resources."

The administration has been responding to a historic flood of children caught crossing the border. In 2011, Border Patrol agents caught fewer than 4,000 children from El Salvador, Guatemala and Honduras. So far this year, they've apprehended nearly 40,000.

Obama has been trying to balance the government's immediate need to care for those children while they're in U.S. custody with a stern message of deterrence, trying to tell their parents back home that their children will not get a free pass to stay in the country.

As part of that enforcement message, White House officials are expected to request a change in the federal law that dictates how the government has to care for children coming from Central America. They did not include that request in Tuesday's funding request, but officials say they will still seek that change.

"The law will be enforced," White House press secretary Josh Earnest said Monday. "And what that means is it means that these children who have been apprehended will go through the immigration court process and if they are found to not have a legal basis for remaining in this country, they'll be returned."

The request includes money for several agencies that have been responding to the surge, including:

• $1.8 billion for the Department of Health and Human Services to better house and care for children and for adults caught traveling with their children. As Border Patrol stations have overflowed with children, HHS has scoured the country to find suitable housing for the kids. They've even used Department of Defense facilities in Texas, California and Oklahoma to house them as they seek more options.

• $1.6 billion for the Department of Homeland Security and the Department of Justice to improve border security and to send more judges, U.S. attorneys and asylum officers to speed up the cases of people caught crossing the border. The border security request includes more money for overtime for Border Patrol agents and more aerial surveillance along the border, including 16 new crews to operate drones. The enforcement request would focus on speeding up the resolution of deportation hearings — either an approval to stay in the country or an order of removal — that are facing lengthy backlogs in U.S. courts today.

• $300 million for the State Department to assist the Central American countries improve their security situations, which is driving much of the rush out of their countries. It would also help them improve "repatriation centers" that are used to take in the deported children and return them safely to their families.

Contributing: David Jackson and Kelly S. Kennedy.