WASHINGTON (AP) — Republican apprehension over President Donald Trump's next tweet and fear of riling conservative voters are undermining GOP leaders' election-year struggle to shove an immigration bill through the House this week, leaving prospects dubious.

Party leaders are trying to finally secure the votes they need for their wide-ranging bill with tweaks they hope will goose support from the GOP's dueling conservative and moderate wings. But more importantly, wavering Republicans want Trump to provide political cover for immigration legislation that's despised by hard-right voters. His recent statements on their bill and history of abruptly flip-flopping on past health care and spending measures have not been reassuring.

Last Tuesday, he privately told House Republicans that he backed their legislation "1,000 percent" and would protect them during their campaigns, lawmakers said. By Friday, he was tweeting that "Republicans should stop wasting their time on Immigration" and wait until after the November elections, when he said the GOP would approve tougher legislation because it will gain strength in Congress. That proposition is dicey at best.

"I think that the best way to pass legislation is to consistently support a position and help move it forward," Rep. Greg Walden of Oregon, a senior House Republican. Asked if Trump was doing that, Walden pivoted toward a door and said: "I'll leave it at that."

Rep. Mike McCaul, R-Texas, the chairman of the House Homeland Security Committee, said on "Fox News Sunday" that he talked to the White House on Saturday and "they say the president is still 100 percent behind us."

The bill would make citizenship a possibility for "Dreamer" immigrants brought illegally to the U.S. when young. It would also finance Trump's aspirational $25 billion wall with Mexico and curb government agencies from wrenching migrant children from detained parents.

The measure is the product of weeks of bargaining between party conservatives and moderates. Even so, the two GOP factions have been unable to resolve their final differences and vote-counters have yet to round up a majority. Republicans are getting no help from Democrats, who uniformly oppose the legislation.

The GOP divisions come at a bad time for the party: Elections are approaching and immigration has riveted public attention for months. Republicans who are battling to retain House control have hoped to focus this fall's campaigns on the economy and tax cuts.

Instead, Republican blockades against ending deportations of young immigrants brought to the U.S. illegally as children were major news earlier this year. In recent days, the focus has shifted to the Trump administration's wrenching of migrant children from their parents.

Neither of those have been good looks for Republicans from swing districts with large numbers of moderate voters — the very incumbents who must be re-elected for the GOP to retain House control.

Lawmakers said leaders wanted to round up GOP votes by adding provisions requiring companies to verify workers' citizenship, which conservatives like. They would also ease restrictions on seasonal migrant workers, a priority for farm-district, moderate Republicans.

Until now, party leaders have hesitated to include those items because they could end up costing votes, not gaining them. Moderate Republicans don't like the citizenship verification requirement and some conservatives don't like helping immigrants stay in the U.S.

Another problem is the two additional provisions don't address the major reason for GOP defections: Conservatives say helping Dreamers stay in the U.S. is handing amnesty to lawbreakers.

"I'm a 'no,'" said Rep. Paul Gosar, R-Ariz., a member of the hard-right House Freedom Caucus. He said he couldn't defend helping the Dreamers "to people waiting in line the right way" to immigrate to the U.S.

The House defeated a more conservative immigration alternative last week.

GOP leaders said the House will vote on its compromise immigration bill despite Trump's flashing red light on the subject.

Top Republicans have wanted to hold the votes, win or lose, partly to defuse an effort by GOP moderates to force the chamber to vote on liberal-leaning bills helping immigrants win citizenship. Those measures could pass the House backed by Democrats and a few Republicans, an outcome that would enrage conservative voters.

In addition, some Republicans are eager for roll calls to show voters back home that they've tried to address the issue.

"I think it's important that the House be able to show we can take the action," said House Majority Leader Kevin McCarthy, R-Calif.

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Associated Press writer Ken Thomas contributed to this report.