House Republicans Friday were mulling a border supplemental spending bill that would give President Obama only a fraction of his $3.7 billion request, but a looming fight over a 2008 deportation law now threatens to derail any deal at all.

Democrats were already likely to balk at the small size of the $900 million spending package Republicans are currently mulling. But Democrats have complicated the deal by walking back their initial support for provision in the bill that would make it easier to speed deportations of children back to their homes in Central America.

President Obama endorsed the change in a June 30 letter to Congress, asking them for the power to fast-track deportations of children back to home countries that don't border the United States. The president is confronted with an unprecedented surge at the border. Federal officials said 61,000 unaccompanied minors have come here since October, most from Honduras, El Salvador and Guatemala.

A 2008 law aimed at curbing sex trafficking, however requires minors who arrive here from noncontiguous countries to receive court hearings that can take years due to a significant backlog.

Like Obama, Democrats initially seemed amenable to the change in the law, which was passed when far fewer minors were crossing into the United States.

In a July 10 interview with reporters, House Minority Leader Nancy Pelosi, D-Calif., said while she does not personally support changing the law to speed deportations, “It's not a deal breaker.”

But both Democrats and Obama changed their stance after an angry backlash from immigrant rights advocates and others, including the American Civil Liberties Union, who said changing the law could endanger the children and deny them due process.

“That would be a very bad thing, not just for the kids who would be sent back to the dangerous conditions they risked their lives to escape, but for the nation and what it says about how we treat the most vulnerable among us,” ACLU policy adviser Georgeanne M. Usova wrote earlier this month.

Obama has gone suddenly silent on the issue, while most Democratic lawmakers say they now oppose changing the law.

The Senate bill, authored by Appropriations Chair Barbara Mikulski, D-Md., leaves out any mention of the 2008 deportation law. Mikulski said a provision to change the law doesn't belong in an appropriations measure.

Pelosi echoed Mikulski on Friday.

If Republicans want to change the law, Pelosi said, they should take it up in separate legislation and leave it out of the border spending package.

“I very firmly believe that it would be a mistake for us to do immigration law in a supplemental bill,” Pelosi said. “You’re not supposed to be legislating on an appropriations bill.”

House Republicans, meanwhile, plan to put a provision to change the law in their funding bill.

That would leave the House bill at odds with the Senate legislation and it likely means House Republicans will need most of their members to back the bill, since Democrats won’t vote for it because of the provision.

With a group of conservative House Republicans opposed to giving Obama any money at all, the fate of the bill is now uncertain.

House legislation hasn’t been scheduled for a floor vote next week, the final days before Congress adjourns for the summer.

“Members should be prepared for possible consideration,” House Minority Whip Kevin McCarthy, R-Calif., said Thursday.