WASHINGTON (AP) — The White House is threatening to veto a $4.5 billion House bill aimed at improving the treatment of migrant families detained after crossing the U.S. southern border, saying the measure would hamstring the administration’s border security efforts and raising fresh questions about the legislation’s fate.

The warning came as Hispanic and liberal Democrats press House leaders to add provisions to the legislation strengthening protections for migrant children, changes that might make the measure even less palatable to President Donald Trump.

Though revisions are possible, House leaders are still hoping for approval as early as today. The Senate planned to vote this week on similar legislation that has bipartisan backing, but many House Democrats say the Senate version’s provisions aimed at helping migrant children are not strong enough. House Democrats seeking changes met late Monday with Speaker Nancy Pelosi, D-Calif.

“Right now, the goal is really to stop — one death is just too much,” said Rep. Adriano Espaillat, D-N.Y., as he left that meeting.

Many children detained entering the U.S. from Mexico have been held under harsh conditions, and Customs and Border Protection Chief Operating Officer John Sanders told The Associated Press last week that children have died after being in the agency’s care. He said Border Patrol stations are holding 15,000 people — more than triple their maximum capacity of 4,000.

Congress plans to leave Washington in a few days for a weeklong July 4 recess. While lawmakers don’t want to depart without acting on the legislation for fear of being accused of not responding to humanitarian problems at the border, it seems unlikely that Congress would have time to send a House-Senate compromise to Trump by week’s end.

In a letter Monday threatening the veto, White House officials told lawmakers they objected that the House package lacked money for beds the federal Immigration and Customs Enforcement agency needs to let it detain more migrants.

Officials also complained in the letter that the bill had no money to toughen border security, including funds for building Trump’s proposed border wall.

“Because this bill does not provide adequate funding to meet the current crisis, and because it contains partisan provisions designed to hamstring the Administration’s border enforcement efforts, the Administration opposes its passage,” the letter said.

Several Democrats said some language they were seeking could end up in separate legislation. Several said changes might include provisions aimed at ensuring that detained children are treated humanely.

“We’ve got lives at stake,” said Rep. Tony Cardenas, D-Calif. He said the U.S. has been “the gold standard” for treating refugees fleeing dangerous countries, “and I don’t think we should compromise that at all.”

The meeting may have helped ease Democratic complaints. Rep. Alexandria Ocasio-Cortez, D-N.Y., told reporters before the meeting that she would oppose the bill but left the door open afterward, saying, “I oppose the situation we’re in, but my main goal is to keep kids from dying.”