Already facing a Democratic insurrection in the House, Senate appropriators are likely to further inflame the debate over a supplemental war spending bill today by adding billions more to the price tag.

House Democratic leaders scrambled Wednesday to secure support for the bill with limited domestic add-ons. But they hinted that they might hold off voting on the nearly $250 billion measure today because of GOP procedural roadblocks.

Even so, the Senate Appropriations Committee appears poised today to try to attach billions of dollars in extra spending that could increase the bill’s chances of being filibustered or vetoed.

Despite pressure from Senate Majority Leader Harry Reid (D-Nev.) and Speaker Nancy Pelosi (D-Calif.) to keep the measure narrowly focused, Senate Appropriations Chairman Robert Byrd (D-W.Va.) plans to offer his domestic spending package that would include almost $4.6 billion in relief for Hurricane Katrina and other natural disasters, $1.2 billion for science programs, about $450 million for highway repairs and hundreds of millions more for food safety and local law enforcement grants, to name a few.

Some Senate Democrats warned that Byrd’s mark and additional amendments could cause the entire process to break down if it appears that the measure has been loaded up. Those Democrats worried that could muddy the original intent of House and Senate Democratic leaders to focus domestic spending on Iraq veterans and the jobless in the hope of making the measure politically difficult for Republicans and the White House to oppose.

“I am sure that appropriators are aware that loading this up like a Christmas tree could put us in a difficult situation with the House [and] the White House, as well as being a PR nightmare,” said one senior Senate Democratic aide.

Still, in question is whether Senate Democratic appropriators will seek to add even more domestic spending at the panel’s markup today.

“There will be some things added. There’s no question about it,” said Appropriations member Sen. Ben Nelson (D-Neb.). “It’s a question of how many and what conditions will there be during the markup, unless there’s a decision made that nothing gets added, which I can’t imagine.”

Others seemed eager to bolster the House measure.

“I think we are very focused on the fact that there are emergencies that are happening in this country that need to be addressed, and how we can deal with that in the package in front of us is important to many of us,” said Sen. Patty Murray (Wash.), an appropriator who also serves in leadership as Senate Democratic Conference secretary. Murray, in particular, was pleased with Byrd’s inclusion of funding for highways.

Despite the Senate committee’s plan to hike the price of the House’s bill, many appropriators insisted that they are worried about a presidential veto and the possibility that Republicans would filibuster a domestic spending package they believe costs too much.

“I think we all understand what the problem is, and the problem is getting a bill that’s clean enough for the president to sign — and by clean enough I mean unencumbered enough that he will sign,” said Sen. Dianne Feinstein (D-Calif.), who sits on the panel. “And that’s kind of the bottom line. Now there are people who probably don’t want him to sign it anyway so it’s hard to figure this thing ahead of time.”

Senate Chief Deputy Minority Whip John Thune (R-S.D.) said Republicans have not yet decided how to respond to the supplemental plans in the House, but he acknowledged that the current House package was causing some “heartburn” among Senate Republicans. They are concerned, he said, about voting against the new GI bill provisions in the bill and not being able to offer their own less-costly version of a veterans’ education bill.

Senate Minority Leader Mitch McConnell (R-Ky.) complained that Democrats appear poised to prevent Republicans from offering amendments on the floor.

“We think the process is extraordinarily flawed in that it has a tendency to unify the minority in opposition simply over the procedure being employed to shut us out and not give us opportunities for alternatives,” McConnell told reporters. He added of the House bill: “Much of it, I think, will be supported by my Conference. But the process, I think, is quite flawed, and there is significant objection to that in my conference.”

Thune said Senate Democrats would make it easier for GOP Senators to oppose the bill if they added more spending.

“I think the more cluttered and convoluted the issue becomes, the easier it’ll be for people on our side to find things they don’t like,” Thune said.

Pelosi, meanwhile, said the House might not vote on the supplemental until next week, blaming Republican delaying tactics on the floor in response to what they said was the majority’s high-handed approach that blocked amendments and a markup.

Democrats were furious when Republicans held a vote open for a considerable amount of time by going to the well and switching their votes back and forth from yea to nay and vice versa.

That prompted Majority Leader Steny Hoyer (D-Md.) to chastise the minority for launching a filibuster by vote-changing, which he called an “abuse of the chair’s forbearance.”

Minority Leader John Boehner (R-Ohio) responded by asserting Republicans’ unhappiness with the way Democrats are handling the supplemental bill and said that they will continue to stand up for the rights of the minority.

“All we’re asking for is to be treated fairly,” Boehner said.

However, Pelosi’s biggest problem Wednesday seemed to be the pressure she faced from within her own party, with some Blue Dog Democrats vowing to oppose the rule for the supplemental because they are upset that the bill fails to pay for the $51.8 billion increase in veterans’ education benefits over 10 years.

“I would not under any circumstances vote for a piece of legislation or a rule that violates” pay-as-you-go rules, said Rep. Allen Boyd (D-Fla.), a co-chairman of the Blue Dog Coalition. “This is a violation of PAYGO. It’s a violation of House rules.”

Boyd said he told House leaders that there isn’t much support from the Blue Dogs for the package, although the group had not taken a formal position.

“I’ve never seen the Blue Dogs this unified and this upset,” added Rep. Jim Cooper (D-Tenn.), who predicted that there would “easily” be enough opposition to violating PAYGO principles.

“A new entitlement is being born,” Cooper said. “We should at least have a birth announcement.”

Pelosi defended adding the funding without offsets given that the war itself has not been offset. “Meeting the needs of our veterans is a cost of war,” Pelosi said. “I think it’s OK for us not to pay for the education of the troops.”

If Blue Dogs are ultimately rolled, House Republicans will be put in a tough spot, given that many Republicans support the GI bill but object to having it joined with extended unemployment benefits.

Minority Whip Roy Blunt (R-Mo.) said leadership would wait to see what ultimately comes to the floor before deciding what to do.

On another front, liberal lawmakers were pushing for additional amendments on war restrictions, although that appeared to be less of a threat to the bill than the Blue Dog revolt.