WASHINGTON — After meeting with the top Senate Republican negotiator on a Homeland Security spending bill, President Donald Trump said Thursday that it is "not an option" for Congress to fail to provide security on the U.S. border with Mexico.

"We'll see what happens but I certainly hear they're working on something, and both sides are moving along," he told reporters at the White House after he met with Sen. Richard Shelby, R-Ala., earlier in the day. "We need border security. We have to have it. It's not an option."

House and Senate negotiators from both parties are racing against a Monday deadline to hammer out a deal that funds the department and increases spending to control illegal immigration and the flow of contraband across the border.

Trump has insisted that he will build a wall between the U.S. and Mexico whether or not Congress grants him the $5.7 billion he has sought for the project, but Speaker Nancy Pelosi has said that she will not sign off an any agreement that provides funding for it.

The president and leading lawmakers in both parties in Congress have voiced support for increasing spending for enhancements to technology for monitoring the border and for improvements to ports of entry to the United States. Trump has said he is considering tapping emergency powers and existing pots of money to build the wall if Congress doesn't give him the cash he wants — a move that both sides see as likely to lead to a court fight.

If Congress and the president don't strike an agreement on border security funding by Feb. 15 — and if they don't pass a stopgap appropriations bill to buy more time — parts of the federal government will shut down for a second time in the last three months.

Trump ended a five-week government shutdown late last month when he announced that he would sign a short-term measure reopening closed federal agencies to give Congress time to negotiate a border-security agreement.