The Senate isn't the only chamber in Congress having problems passing major legislation.

On the same day Senate Republicans admitted they're out of ideas on how to pass a healthcare reform bill, it became clear that House Republicans are having their own difficulties finding GOP votes for the 2018 budget, which is the legislative vehicle for tax reform and other bills.

A plan to take up the budget next week appeared in peril on Tuesday after the most conservative faction of the GOP conference declared it would oppose the plan because, they said, it does not sufficiently reduce domestic spending, among other reasons.

Rep. Mark Meadows, R-N.C., who heads the conservative Freedom Caucus, told the Washington Examiner that more than three dozen conservative GOP lawmakers are prepared to vote against the Republican budget, in part because they believe the measure's $203 billion in domestic spending cuts are not enough of a reduction.

"I don't see them putting it on the floor," Meadows told the Washington Examiner Tuesday.

Conservative opposition is enough to sink the bill, which will get no Democratic support and must pass entirely with Republicans. "The hope is to move it as soon as possible," a Republican aide said when asked about the budget.

The House budget is scheduled for a vote in committee on Wednesday, where it is expected to pass with two or three Republicans voting against it. Budget Committee Chairwoman Diane Black, R-Tenn., told reporters the bill would get a House floor vote after passing the committee.

But Majority Leader Kevin McCarthy, in an interview with the Washington Examiner, made no promises.

"We'll whip it and understand where it's at," said McCarthy, R-Calif.

In addition to budget problems, rank-and-file Republicans are generating opposition to a bill that would reauthorize the Federal Aviation Administration because they oppose a provision that would privatize the nation's air traffic control system.

House Republican leaders hoped to pass both the budget and the FAA measure by next week, which is the last legislative session prior to the five-week August recess. But neither measure is guaranteed to get vote at this point.

House Speaker Paul Ryan, R-Wis., tried to build support for the FAA bill in a private meeting with Republican lawmakers on Tuesday. But GOP lawmakers have been pummeled with opposition material from special-interest groups representing the general aviation industry, who fear privatization of the air traffic control system lead to higher user fees.

"Such a scenario would be very harmful to business aviation," the National Business Aviation Association said in a statement. "Access to airports, and to the nation's airspace, creates jobs, generates economic activity and helps make America's aviation system work for all Americans."

Opponents are also warning lawmakers that privatization would threaten the security of military aviation by giving a nongovernmental group control. Republicans abandoned plans to take up the FAA bill this week after a whip count showed a lack of support, in part due to the military security fears.

It's not clear when the FAA bill will come up now. If it stalls, it will be the second time in two years the privatization effort has been sidelined.

"Our whip team and the chairman continue to have productive conversations with members about this legislation," a spokesperson for Majority Whip Steve Scalise, R-La., told the Washington Examiner on Tuesday.

President Trump supports privatizing the air traffic control system and touted it at a White House ceremony earlier this year.

The system desperately needs modernization, and proponents of privatization say it can happen much faster by removing it from the control of the FAA and awarding it to a board made up of airline industry representatives.

Ryan also backs privatization and is working to win over the rest of the GOP. But for some Republicans, the security issue is just too big.

"I am all for modernization, but I am against privatization," Rep. Ralph Abraham, R-La., told the Washington Examiner. "My concern really boils down to national security."

The House Transportation Committee Tuesday began circulating background material on the privatization provision that is aimed at assuring lawmakers national security will not be jeopardized or taken over by a private air traffic control board.

"The new entity will provide a service and nothing more," the memo said. Supporters also point out that Secretary of Defense James Mattis supports the plan.

But House Republicans see an uphill battle for the provision and note that a Senate FAA reauthorization measure does not include privatizing air traffic control.

"It's dead on arrival there," Abraham said.