WASHINGTON (AP) — Calls are mounting on Capitol Hill for the Trump administration to end the separation of families at the southern border ahead of a visit from President Donald Trump to discuss legislation.

Trump's meeting late Tuesday afternoon with House Republicans comes as lawmakers in both parties are up in arms over the administration's "zero tolerance" approach to illegal border crossings.

Under the policy, all unlawful crossings are referred for prosecution — a process that moves adults to the custody of the U.S. Marshals Service and sends many children to facilities run by the Department of Health and Human Services. Under the previous administration, such families were usually referred for civil deportation proceedings, not requiring separation.

Nearly 2,000 children were separated from their families over a six-week period in April and May.

The fight is erupting as the House is already embroiled in an election-year struggle over immigration legislation that threatens to hurt Republicans in November.

Democrats have seized on the family separation issue, swarming detention centers in Texas to highlight the policy. They are demanding that the administration act to keep migrant families together. Republicans are increasingly joining Democrats in that call.

Michigan Republican Rep. Fred Upton called for an immediate end to the "ugly and inhumane practice," adding, "It's never acceptable to use kids as bargaining chips in political process." Kansas GOP Sen. Pat Roberts said he is "against using parental separation as a deterrent to illegal immigration."

"The time is now for the White House to end the cruel, tragic separations of families," Sen. Lisa Murkowski, R-Alaska, said in a statement.

The Trump administration insists the family separations are required under the law. But after signaling Monday that it would oppose any fix aimed solely at addressing the plight of children separated from their parents under the crackdown, the White House said Tuesday that it is reviewing emergency legislation being introduced by Sen. Ted Cruz, R-Texas, to keep migrant families together.

Asked if the White House supports the Cruz measure, Mercedes Schlapp, director of strategic communications, told reporters "we're looking into the legislative text on the Cruz bill."

The senator's bill would add more federal immigration judges, authorize new temporary shelters to house migrant families, speed the processing of asylum cases and require that families that cross the border illegally be kept together, absent criminal conduct or threats to the welfare of any children.

At a White House briefing Monday, Homeland Security Secretary Kirstjen Nielsen declared, "Congress alone can fix it." That line has been echoed by others in the administration, including Trump, who has falsely blamed a law passed by Democrats for the "zero tolerance" approach to prosecutions of families crossing the border.

Two immigration bills under consideration in the House could address the separations, but the outlook for passage is dim. Conservatives say the compromise legislation that GOP leaders helped negotiate with moderates is inadequate.

Rep. Jim Jordan, R-Ohio, a member of the Freedom Caucus, said he's skeptical that even a full-throated endorsement from Trump will be enough to get the compromise bill through the House.

The compromise bill shifts away from the nation's longtime preference for family immigration to a new system that prioritizes entry based on merits and skills. It beefs up border security, clamps down on illegal entries and reinforces other immigration laws.

To address the rise of families being separated at the border, the measure proposes keeping children in detention with their parents, undoing 2-decade-old rules that limit the time minors can be held in custody.

Rep. Dave Brat, R-Va., another Freedom Caucus member, said he expects the GOP compromise bill to be defeated if it reaches the floor. "There's not enough votes because it doesn't solve the problem," he said.

Faced with the prospect of gridlock in the House, senators appear willing to take matters into their own hands.

Sen. John Cornyn of Texas, the No. 2 Republican leader, said Senate Republicans are working on language to address the family separations that could receive a floor vote, potentially as part of a spending bill package.

"I don't think the answer to family separation is to not enforce the law. I think the answer to family separation is: Don't separate families while you're enforcing the law," Cornyn told reporters. "It's all within our power, and people have to overcome their desire to preserve an issue to campaign on."

Sen. Chuck Grassley of Iowa, the Republican chairman of the Judiciary Committee, said he wants to do away with a legal settlement that requires the government to release children from custody and to their parents, adult relatives or other caretakers, in order of preference.

GOP senators including Lindsey Graham of South Carolina, Jeff Flake of Arizona and Susan Collins of Maine also said they've been discussing family separation legislation.

Graham told reporters the measure would keep migrant families together, provide additional judges so detained families would face shorter waiting periods, and supply facilities for the families to stay. He said he did not know how much the proposal would cost.

The administration, meanwhile, is hoping to force Democrats to vote for the bills or bear some of the political cost in November's midterm elections. Democrats brushed aside that pressure.

"As everyone who has looked at this agrees, this was done by the president, not Democrats. He can fix it tomorrow if he wants to, and if he doesn't want to, he should own up to the fact that he's doing it," said Senate Democratic leader Chuck Schumer of New York.

Senate Democrats have rallied behind an immigration bill from Sen. Dianne Feinstein, D-Calif.  Her bill would prohibit the separation of migrant children from their parents, with exceptions for findings of child abuse or trafficking. If separations occur, Homeland Security would have to provide clear guidelines for how parents can contact their kids.

One House Republican in a swing district, Rep. Mike Coffman of Colorado, said he's willing to endorse the Feinstein bill if that's what it takes.

"I reached out to Sen. Feinstein's office to let her know I want to help her put a stop to this human rights disaster at the border. If that means introducing her bill in the House, I'd be honored to stand with her," he said.

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See AP's complete coverage of the debate over the Trump administration's policy of family separation at the border: https://apnews.com/tag/Immigration