President Barack Obama is seeking $2 billion in emergency funds to curb the influx of women and children fleeing Central America and illegally entering the United States.
In addition, Obama will seek greater authority for U.S. immigration officials to speed up the deportation of children caught crossing from countries such as Guatemala, Honduras and El Salvador, the official said.
The request will mark a dramatic increase in Obama's attempt to gain control of a chaotic scene on the U.S. border with Mexico where tens of thousands of children have crossed without their parents, straining resources and creating a political and humanitarian crisis.
House Minority Leader Nancy Pelosi visited a Border Patrol facility in Brownsville on Saturday that held unaccompanied children.
Pelosi said the U.S. must deal responsibly with the influx of children. "We have a moral responsibility to address this in a dignified way."
More than 52,000 unaccompanied children and 39,000 women and children from Central America have been apprehended entering the U.S. illegally since October.
Obama plans to make the requests of Congress in a letter to be sent Monday, a White House official said.
Details of the emergency appropriation, including the exact amount and how it would be spent, will come after lawmakers return from their holiday recess on July 7, the official said.
Obama will also ask Congress to increase penalties for the so-called "coyotes" who smuggle children across the border and profit from it, the official said.
The official said Obama will also request a "sustained border security surge through enhanced domestic enforcement," along with an increase in immigration judges to more speedily adjudicate the cases of recent border crossers.
Obama will step up efforts with Central American countries to repatriate migrants who are returned to their home countries and address the root causes of migration.
And, the official said, he will seek "the resources necessary to appropriately detain, process and care for children and adults."
In an ABC interview last week Obama urged Central American parents not to let their children leave on a frequently hazardous trip to the United States, but his words have so far had little impact.
In Brownsville, Pelosi said she holds little hope that Congress will pass comprehensive immigration reform this year but that politics should be set aside.
"A few days ago I would have been more optimistic about comprehensive immigration reform," Pelosi said. "I thought that we had been finding a way because we have been very patient and respectful of [Speaker of the House John Boehner] trying to do it one way or another. I don't think he gives us much reason to be hopeful now, but we never give up. There's still the month of July."
Congressional Republicans have expressed outrage at the Obama administration's handling of the crisis, accusing the government of letting the children into the country to pile pressure on Congress to approve a long-stalled immigration overhaul.
This past week, a leading House supporter of policy changes said legislative efforts on the issue were dead.
Rep. Luis Gutierrez of Illinois, who's been one of the most bullish Democrats about the chances for action, said he had given up.
Boehner's office did not immediately respond to a request for comment Saturday.
The Border Patrol in South Texas has been overwhelmed for several months by an influx of unaccompanied children and parents traveling with young children from Honduras, Guatemala and El Salvador.
Unlike Mexican immigrants arrested after entering the U.S. illegally, those from Central America cannot be as easily returned to their countries.
The U.S. had only one family detention center in Pennsylvania, so most adults traveling with young children were released and told to check in with the local immigration office when they arrived at their destination. A new facility for families is being prepared in New Mexico.
Children who traveled alone, like those visited by Pelosi in Brownsville, are handled differently.
By law, they must be transferred to the custody of the Health and Human Services Department within 72 hours of their arrest. From there, they are sent into a network of shelters until they can be reunited with family members while awaiting their day in immigration court.
Some information for this report provided by Reuters and AP.