Calls are mounting in Washington for the Trump administration to end the separation of families at the southern border ahead of a visit from Donald Trump to discuss legislation.

The president’s meeting with House Republicans comes as legislators 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 US 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 comes with the House already embroiled in an election-year struggle over immigration legislation that threatens to damage Republicans in November.

Democrats have seized on the family separation issue, swarming detention centres in Texas to highlight the policy.

They are demanding that the administration act to keep migrant families together, and Republicans are increasingly joining that call.

The Trump administration insists the family separations are required under law, but after signalling on 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 on Tuesday it is reviewing emergency legislation to keep migrant families together.

The bill would add more federal immigration judges, authorise new temporary shelters to house migrant families, speed the processing of asylum cases and require that families that cross the border illegally to be kept together, if there is no criminal conduct or threats to the welfare of children.

At a White House briefing on Monday, homeland security secretary Kirstjen Nielsen said: “Congress alone can fix it.”

That line has been echoed by others in the administration, including Mr 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 Republican leaders helped negotiate with moderates is inadequate.