Republican lawmakers on Thursday were unsure of whether they would be able to find the votes to pass their 2018 budget plan anytime soon, even though the plan was easily approved in the House Budget Committee a day earlier.

The GOP needs a budget to pass tax reform this year, since the budget will set up privileged legislation on tax reform that couldn't be filibustered by Democrats in the Senate.

Majority Leader Kevin McCarthy did not schedule the fiscal year 2018 budget resolution "Building a Better America, for a vote next week, which is the final legislative session before a scheduled five-week recess.

McCarthy told the Washington Examiner GOP leaders are going to determine the level of Republican support for the measure, which is to serve as the legislative vehicle for tax reform, a top Republican agenda goal. Conservatives and moderates are at loggerheads over the size of domestic spending cuts, and lawmakers are also clamoring for information about the undisclosed tax plan that is to serve as the centerpiece of the legislation.

"We are working through it," McCarthy told the Washington Examiner.

Prospects for the measure were bolstered Wednesday night when the House Budget Committee passed it along party lines without any Republican defectors, even though some conservative critics sit on the panel.

Conservative Dave Brat, R-Va., was among the lawmakers who voted for the bill after criticizing it. Brat was seeking to double the $203 billion in domestic spending cuts called for in the $4 trillion plan and said he has not decided whether he will back the bill on the House floor.

"We should have done more to tackle mandatory spending levels in this budget," Brat said in a statement. "While I am not happy with some of this budget product and am not yet prepared to vote for it on the House floor, passing it out of committee is an important step in keeping our promise to keep tax reform momentum and get it on President Trump's desk. I hope conservative concerns can be adequately addressed through an amendment process on the House floor."

Another Budget Committee Republican who voted for the plan, Rep. Mark Sanford, R-S.C., may not vote for final passage, a GOP aide said.

Rep. Mark Meadows, R-N.C., who is chairman of the conservative House Freedom Caucus, told the Washington Examiner that more than three dozen lawmakers do not support the budget plan, which is enough to sink the legislation since it must pass entirely with GOP votes.

Moderate Republicans, meanwhile, say the spending cuts in the budget are too steep.

"I've got concerns," Rep. Charlie Dent, R-Pa., told the Washington Examiner.

No Democrats back the plan, in part because it cuts domestic spending and spends more on defense. The GOP plan would fund the domestic discretionary budget at $511 billion and the defense budget at $621.5 billion.

Meadows noted that the House has begun the process of passing 2018 spending bills, moving forward without waiting for a budget resolution to pass. In that way, the budget plan doesn't matter much to Republicans as a guide for upcoming spending bills.

"We are already appropriating, so it doesn't matter," Meadows said.

But the budget does matter to Republicans because it will set up a path for tax reform legislation that can be more easily passed in the Senate under the so-called reconciliation process. For that reason, Meadows believes Republicans should drop plans for a budget until they develop a tax reform plan and then try to pass the budget.