WASHINGTON -- The Republican-led House resoundingly rejected a far-ranging immigration bill on Wednesday despite an eleventh-hour endorsement by U.S. President Donald Trump, as the gulf between the GOP's moderate and conservative wings proved too deep for leaders to avert an election-year display of division.

The bill was killed 301-121, with nearly half of Republicans opposing the measure. The depth of GOP opposition was an embarrassing showing for Trump and a rebuff of House leaders, who'd postponed the vote twice and proposed changes in hopes of driving up the tally for a measure that seemed doomed from the start.

The roll call seemed to empower GOP conservatives on the fraught issue. Last week a harder-right package was defeated but 193 Republicans voted for it, 72 more than Wednesday's total. Another 112 Republicans voted "no."

"We need to start securing the border and not reward bad behaviour, and that's what this bill did," said Rep. Roger Williams, R-Texas. Conservatives have opposed the bill's provision offering a chance at citizenship for hundreds of thousands of immigrants who came to the U.S. illegally as children, and have said it doesn't do enough to limit the relatives who immigrants here legally can sponsor for residence.

Even if it passed, the House bill rejected Wednesday would have been dead on arrival in the closely divided Senate, where Democrats would have had enough votes to kill it. House Democrats voted unanimously against it.

"Show some compassion," said Rep. Adriano Espaillat, D-N.Y., who came to the U.S. from the Dominican Republic with his parents at age 9. "Will we step up to be the country that allowed me, as a young boy, to find safety with my mother and father?"

GOP leaders have been talking about a Plan B: a bill focused narrowly on barring the government from wresting children from migrant families caught entering the country without authorization. With television and social media awash with images and wails of young children torn from parents, many Republicans have wanted to pass a narrower measure addressing those separations before Congress leaves at week's end for its July 4 break.

But that seemed unlikely. GOP aides said Republicans had yet to agree on bill language, and the effort was complicated by a federal judge who ordered that divided families be reunited with 30 days. Republicans have been working on legislation that would keep migrant families together by lifting a court-ordered 20-day limit on how long families can be detained.

Rep. Cathy McMorris Rodgers, R-Wash., a member of the GOP leadership, said she will work with the administration and lawmakers on "a solution that addresses the problem in the most practical and appropriate manner, especially in light of yesterday's court decision."

Besides creating a pathway to citizenship for some young immigrants, the defeated bill would provide $25 billion for Trump to build his coveted wall on the border with Mexico. It would restrict family-based immigration and bar the Homeland Security Department from taking migrant children from parents seized crossing into the country without authorization.

In a startling turnabout earlier Wednesday, Trump made an all-caps pitch for the bill. Last Friday, he'd urged Republicans to stop wasting time on the effort until after the November elections.

In his latest display of whiplash on the issue, "HOUSE REPUBLICANS SHOULD PASS THE STRONG BUT FAIR IMMIGRATION BILL, KNOWN AS GOODLATTE II, IN THEIR AFTERNOON VOTE TODAY, EVEN THOUGH THE DEMS WON'T LET IT PASS IN THE SENATE."

The tweet -- which referenced Rep. Bob Goodlatte, R-Va., one of the bill's sponsors -- was the latest example of Trump's erratic dealings with Congress. On Friday he dashed off a tweet, saying Republicans should "stop wasting their time on Immigration until after we elect more Senators and Congressmen/women in November."

The White House also sent a letter to lawmakers Wednesday formally stating its support, saying the legislation would "support the administration's goals" on immigration.

The vote caps months of futile GOP efforts to pass wide-ranging legislation on an issue that could colour scores of congressional races in this fall's contest for House and perhaps Senate control. The Senate rejected three proposals in February, including one reflecting Trump's hard-line policies and two bipartisan plans.

Democrats and centrist Republicans from swing districts say the GOP could suffer because the party, steered by Trump's anti-immigrant harangues, could be alienating pivotal moderate voters. But conservatives relish such tough stances. And rather than achieving middle ground, leaders' efforts have largely underscored how irreconcilably divided the GOP is on the topic.

Conservative Rep. Steve King, R-Iowa, said lawmakers "couldn't go home and face their constituents and say 'I just gave you the largest amnesty ever without really a guarantee of enforcement."' Conservatives consider the possibility of citizenship for immigrants who arrived illegally to be amnesty.

Leaders flirted with adding provisions aimed at winning votes, helping migrant farmworkers to stay longer in the country and gradually requiring companies to use an electronic database to verify their employees' U.S. citizenship. But they abandoned the plan, which would have made the vote even more uncomfortable for moderates opposing the database.

Rep. Carlos Curbelo, R-Fla., and Rep. Jeff Denham, R-Calif., from districts with large numbers of Hispanic voters, helped force Ryan to stage immigration votes.

This spring they launched a petition that could have led to House passage of liberal-leaning measures creating a pathway to citizenship, bills backed by Democrats but opposed by most Republicans. Leaders headed off the petition by urging GOP lawmakers to not sign it, partly by crafting the compromise package the House rejected Wednesday.

The more conservative bill the House rejected last week clamped down on legal immigration and provided no way for the young immigrants to become citizens.

Trump has issued an executive order reversing his own family separation policy, but around 2,000 children remain removed from relatives.

The Senate is trying craft bipartisan legislation keeping families together.

AP reporters Catherine Lucey and Kevin Freking contributed.