House Democrats reacted with anger and frustration to the news Tuesday of President Trump's plans to divert billions of dollars in military funding to border wall construction and lamented not having done more to stop it from happening.

Following a Washington Post report late Monday on the White House's plans to take $7.2 billion in Pentagon funding in the fiscal 2020 budget to build more fence at the U.S.-Mexico border, Rep. Joaquin Castro of Texas said Democrats should have fought harder to block Trump from redirecting appropriated money.

"I voted against that appropriations bill for one reason because it didn't contain any restraints on the president transferring the money. I anticipated that would always be problematic," Castro, chairman of the Congressional Hispanic Caucus, told reporters on Capitol Hill Tuesday morning. "I think we should have fought for language that restrained the transfer of that money."

Rep. Debbie Wasserman Schultz, a Florida Democrat and chairwoman of the House Appropriations Subcommittee on Military Construction, Veterans Affairs, and Related Agencies, said House Democrats pushed Senate Republicans "as far as we could" when both chambers went to conference. "It was among the last things that were finalized. We could not have pushed it harder," she said.

Lucille Roybal-Allard, chairwoman of the House Appropriations Subcommittee on Homeland Security, said lawmakers' hands were tied from the start.

"It doesn't matter what the Congress does. The president does whatever he pleases," Roybal-Allard told reporters. "Hopefully, the courts will rule in our favor."

This year, Democrats agreed to allow wall funding and other border security budget numbers to remain at 2019 levels of $1.375 billion, which satisfied Republicans but was far less than the $8 billion Trump had requested. The bill also allowed him to transfer money from other parts of the federal budget.

Last February, Trump took more than $6 billion from other parts of the federal budget and used the money to construct the border wall in an effort to fulfill his campaign promise to erect more barrier along the 2,000-mile southern border between Texas and California.

Many House Democrats voted against the measure in the House due to their objection to the border wall and border security funding, but it cleared Congress thanks to bipartisan support.

Part of last year's redirected money has been stalled in court, but an appeals court judge in El Paso, Texas, earlier this month allowed the government to continue construction while the case continues. Once the White House requests the transfer of military funds, the Trump administration will have used more than $18 billion for border fence construction.

To date, 100 miles of fence have gone up, though nearly all of it is replacing older fence or is a backup fence system that stands behind the original barrier. The Department of Homeland Security has vowed 500 miles of completed fence by December, though last week, acting DHS Secretary Chad Wolf promised between 400 to 450 miles.

The White House and Pentagon did not respond to requests for comment.

[Opinion: Weekly Trump Report Card: ‘Dizzying,’ with wins on border wall and deregulation]