Homeland Security Secretary Kirstjen Nielsen said Tuesday that she doesn't believe President Trump will be able to extend the Deferred Action on Childhood Arrivals program past March 5.

There were some indications last year that Trump would be willing to extend DACA if Congress were unable to agree on how to legislate the program that until now was a unilateral plan put in place by former President Barack Obama.

But in a Senate Judiciary Committee hearing, Nielsen said she doesn't believe Trump has that option to help younger immigrants brought to the U.S. illegally as children.

"I believe the Attorney General has made it clear that he believes such exercise is unconstitutional," she said after Sen. Lindsey Graham, R-S.C., asked her if Trump has the legal authority to extend it. "It's for Congress to fix."

Graham also asked her if Trump was thinking of an executive order to extend DACA.

"Not that I am aware of," she said.

Nielsen's comments would seem to raise the pressure on lawmakers to find an agreement on how to legislate a new DACA plan. Republicans and Democrats are still at odds over how to get that done, as Republicans are demanding border security measures as part of the package, and Democrats have refused those demands.

Republicans specifically want border security and funding for a border wall, an end to chain migration, and an end to the visa lottery system.

There is added pressure in the negotiations, as many Democrats want a final immigration package included in a short-term spending bill that must pass this week. But a deal is unlikely by Friday.

At the hearing, Graham said he agreed with Nielsen's assessment that Trump cannot extend DACA, and said that's a reason why lawmakers should reach a deal.

"I don't believe the president can extend this by executive order, and March 5, a lot of bad things begin to happen," Graham said. "Seems to me we ought to try to avoid that if we can. Do you agree with that?"

"Yes sir," Nielsen said.