WASHINGTON (AP) — A fight between President Donald Trump and Democrats over hurricane relief for Puerto Rico is imperiling a widely backed disaster aid bill that is a top priority for some of Trump's Southern GOP allies.

The amount of money in dispute is relatively small, but Trump feels antipathy toward the U.S. territory's government and Senate Republicans are taking a hard line — for now — in denying Democratic demands for more aid for Puerto Rico, which was devastated by back-to-back hurricanes in 2017.

Democrats are threatening to block the GOP bill in a showdown Senate vote on Monday afternoon. What would happen next is unclear, but top Senate Democrat Chuck Schumer of New York appears confident that a successful filibuster won't kill the bill outright, but instead drive Trump and Senate Majority Leader Mitch McConnell toward compromise.

The $13.5 billion Senate measure mostly mirrors a $14.2 billion measure passed by the House in January, combining aid to Southern farmers, California communities devastated by last summer's wildfire, and rebuilding help for hurricane-hit states such as Florida, Georgia and North Carolina.

Democrats want to add almost $700 million more to unlock further disaster aid for Puerto Rico and several states and to help them rebuild badly damaged water systems. Democrats are also seeking language to force the administration to release billions of dollars in rebuilding funds that have already been approved.

McConnell, R-Ky., however, has maneuvered to shut off any opportunity for Democrats to amend the bill.

"I think that's a mistake. I think we have a good package that the House would accept. If we could bring it onto the floor and have a vote on it I think it would pass," said Sen. Patrick Leahy of Vermont, the Democrats' point man on the legislation. "These are Americans who are suffering. I think we ought to be able to come together on it. So I think it's unfortunate to have just a take-it-or-leave-it bill."

The parliamentary setup, however, is complicated and gives Democrats some advantages. And the political momentum for the measure — strongly backed by Trump's allies in Georgia, Florida, and North Carolina, among other states — has only been heightened by the outbreak of massive flooding in Midwestern states such as Iowa and Nebraska.

Trump has yet to veto a spending bill despite some tough talk and he has signed off on $600 million to ease food stamp cuts in Puerto Rico. But he poor-mouthed the island's government at a meeting with Senate Republicans last week and suggested Puerto Rico has gotten too much disaster help compared with states such as Texas.

"I have taken better care of Puerto Rico than any man ever. We have $91 billion going to Puerto Rico. We have $29 billion to Texas and $12 billion to Florida for the hurricane," Trump said Thursday. "They have to spend the money wisely. They don't know how to spend the money and they're not spending it wisely."

Trump's $91 billion estimate, said a White House spokesman, includes about $50 billion in expected future disaster disbursements, along with $41 million that's already been approved.

Caught in the middle are pragmatic Republicans such as Appropriations Committee Chairman Richard Shelby of Alabama, who is looking for a deal. Democrats controlling the House have made it clear that the measure won't clear Congress for Trump's signature without additional money for Puerto Rico and badly needed Medicaid funding for the Northern Mariana Islands.

"Let's hope that between now and next week we can keep talking and reach something," Shelby told reporters. "This is a three-legged stool. The House, the Senate and the president are involved in this."

"There's always more you can do, but we need to get this done," said Sen. Rick Scott, R-Fla. "I think Schumer is just playing politics."