WASHINGTON – Dallas Rep. Jeb Hensarling, head of a conservative bloc that wants to rein in federal spending, went to the Oval Office on Wednesday afternoon with a pledge to President Bush: We've got your back.

Mr. Bush is heading for a budget confrontation this fall with Democrats, and the Hensarling-led Republican Study Committee is giving him extra leverage by collecting pledges from enough House members to uphold a veto.

"The president now has insurance, and House conservatives are relevant in the debate about whether we'll protect the family budget. We're partners with the president in sustaining his veto," Mr. Hensarling said on the White House driveway after a meeting with Mr. Bush and top House GOP leaders.

Mr. Bush wants to hold discretionary spending to $933 billion in fiscal 2008. That's up about $60 billion from this year.

But Democrats say the Bush budget would shortchange education, health care and other domestic priorities, and they're demanding an additional $23 billion, prompting Republicans to step up complaints about "excessive spending."

Mr. Bush's veto of a stem cell bill on Wednesday, shortly before the meeting with House Republicans, was only the third time he's wielded that authority.

"I submitted a budget to the Congress that sets priorities. ... It's a budget that keeps taxes low so the economy continues to grow. And it's a budget that will be in balance in five years," he said at the meeting with House Minority Leader John Boehner of Ohio, Mr. Hensarling and others, thanking them for backing him on the veto threat.

Mr. Hensarling, a third-term Dallas lawmaker, isn't formally part of the Republican leadership. But as head of the Republican Study Committee, he leads a core group that makes up more than half the party's House members. With Rep. John Campbell, R-Calif., head of the study committee's budget task force, Mr. Hensarling collected 147 pledges from lawmakers willing to sustain a veto on any spending bill that exceeds Mr. Bush's requests.

It takes two-thirds majorities of the House and Senate to override a veto, and in the House, 146 votes are enough to stymie an attempt.

"Our members literally have signed the dotted line," said House Minority Whip Roy Blunt, R-Mo.

"Rarely have Republicans been as united as they are today in trying to save the family budget from the onslaught of the federal budget," Mr. Hensarling said, asserting that the maneuver would hold down federal spending enough to save the average family $3,000 in taxes.

He acknowledged that conservatives, including him, have long grumbled about a lack of fiscal discipline in Washington – a problem that hasn't been confined to Democrats. "Many of us think that the president's requested levels are too high, but we're partners with him, and it's an important debate to have and an important step to have," he said.

One sign of an impending budget showdown is that Mr. Bush announced this week that he'll replace White House budget director Rob Portman, a former Ohio congressman with a reputation for pragmatism and bipartisan relations, with Jim Nussle, an Iowan who was known for being far more confrontational and ideological when he chaired the House budget committee.