WASHINGTON  —  A Republican "compromise" bill reforming US immigration law failed spectacularly in Congress on Wednesday, dealing a blow to President Donald Trump’s efforts to resolve a swirling border crisis that has seen thousands of migrant families separated.

Lawmakers rejected the Border Security and Immigration Reform Act by an overwhelming 121 to 301, with all Democrats opposing the bill along with dozens of Republican conservatives who argued it did not do enough to rein in illegal immigration.

The collapse is the second ill-fated attempt by divided House Republicans to coalesce around immigration reform, and marks an embarrassment for Trump, who had backed the bill with an 11th hour tweet Wednesday urging its passage.

But the president’s conflicting message in recent weeks, including telling Republicans to "stop wasting their time" on immigration because Democrats would block the bill in the Senate, no doubt threw a wrench into the already contentious effort.

Republicans eager to resolve the crisis -- in which some 2,000 children remain separated from their parents who either have been arrested and referred for prosecution for crossing illegally, or whose asylum cases are being adjudicated -- expressed their frustration at the lack of action.

"Simply put, the House has now missed two opportunities to fix our broken immigration system and make our country more safe, secure, and prosperous,"  House Republican Lloyd Smucker said on Twitter.

"The American people deserve better than the failed status quo."

The rejection now raises the possibility of lawmakers taking up a narrower measure which ends the family separations that began in early May as a result of the administration’s "zero tolerance" policy of prosecuting anyone who crosses the border illegally, even to seek asylum.

But such a measure would not address broader issues like the $25 billion in border wall funding, protections for "Dreamer" immigrants who were brought to the country illegally as children, and curtailment of legal immigration that were included in the failed bill.

Timing for the narrower legislation remained in doubt. Lawmakers are expected to decamp on Friday and head to their home districts for a week-long July 4th recess.

Senator James Lankford, a Republican, urged Congress to negotiate solutions on border security, family separation, more efficient immigration courts, and Dreamers "rather than just complaining" about immigration.

"Although one bill may fail, we must go back to the negotiating table & keep trying," he tweeted.

Trump has made clear he still intends immigration to be at the heart of the battle for November’s midterm elections, urging Republicans to show their commitment to the hard line that got him elected in 2016 -- while ramping up the rhetoric linking weak borders with gang crime, and blaming Democrats for both.

"HOUSE REPUBLICANS SHOULD PASS THE STRONG BUT FAIR IMMIGRATION BILL," Trump tweeted ahead of the vote.

"PASSAGE WILL SHOW THAT WE WANT STRONG BORDERS & SECURITY WHILE THE DEMS WANT OPEN BORDERS = CRIME. WIN!" he tweeted, even as he acknowledged the bill had no chance of getting enough Democratic votes to pass in the Senate.

On Tuesday the president was handed an important -- if largely symbolic -- victory on another key plank of his migration policy as the Supreme Court voted to uphold his controversial travel ban targeting five Muslim-majority nations.

Trump pounced on the decision as "a tremendous success and victory for the American people."

Immigration has long been among the most intractable issues in American politics, with Congress repeatedly failing to pass comprehensive reform.  — AFP