Vice President Mike Pence called the grim conditions in some detention centers for migrant children in U.S. custody "heartbreaking" and "unacceptable," but said there was little his administration could do to remedy them unless congressional Democrats agreed to sign off on more funding and expand detention space.

"We're doing a lot with what the Congress has given us, but again Congress refused to increase the bed space in the last appropriations bill," Pence said on "Face the Nation" Sunday.

"They continue to delay efforts on additional humanitarian support," he added.

Lawyers this week detailed harsh conditions faced by approximately 250 migrant children — including infants — at an overcrowded Border Patrol station in Clint, Texas. According to the attorneys, older children were taking care of the younger ones. Some young mothers had to wear clothes stained with breast milk. The children also did not have access to soap and toothbrushes, and most had not showered since they crossed the southern border.

Border Patrol is supposed to transfer unaccompanied migrant children to the Department of Health of Human Services (HHS) within 72 hours. Lawyers and advocates, however, have documented cases in which some children are being held for longer.

Asked if the American people should come to accept these conditions, Pence replied, "absolutely not."

Still, he reiterated that he believes the problems in detentions centers stem from what he portrayed as a "refusal" by the Democratic-led House to approve the administration's multi-billion-dollar request to fund border enforcement, shelters for unaccompanied migrant children and other efforts to deal with the unprecedented surge of Central American families heading towards the U.S.-Mexico border.

"It's amazing to think that Mexico has done more to secure our southern border in the last 10 days than Democrats have done in the last 10 years," Pence said. "The American people deserve better."

Republicans and Democrats in Congress are currently negotiating legislation to allocate some of the funds to different agencies, including Border Patrol, that the administration has asked for.

In a move that was widely seen as preemptive action to prevent talks from falling part, President Trump on Saturday delayed a wave of roundups of undocumented families which immigration authorities were expected to start carrying out Sunday. He nevertheless threatened to order mass deportations unless congressional Democrats agreed to revamp the nation's asylum laws within two weeks.