A seemingly hopeless divide within the Republican Party over oil drilling in a pristine wildlife refuge in Alaska is threatening to block unrelated budget cuts that are a central pillar of the GOP's plans for this year.

The battle pits about two dozen pro-environment and newly empowered House Republicans against veteran GOP proponents of drilling who say the Arctic National Wildlife Refuge may hold up to $500 billion worth of oil vital to the nation's energy needs. Neither side is budging.

"The Senate won't take anything that doesn't have some sort of program for ANWR in it, and the House right now won't take anything that does," said House Energy and Commerce Committee Chairman Joe Barton, R-Texas.

Year after year, Republican leaders and energy industry supporters like Barton could ignore the two to three dozen House Republicans who opposed drilling in the Alaska refugee because their "no" votes were offset by an equal number of "yes" votes from oil-state Democrats.

But virtually every Democrat in Congress opposes the budget bill because of its cuts in popular social programs, so Republican leaders in the House don't have that critical support from across the aisle to carry the vote on Alaska drilling.

The impasse threatens plans to deliver to its GOP political base by Christmas about $45 billion in spending cuts over the next five years. The base is uneasy with its party's performance on spending and budget deficits. Passage of the budget bill is also an important step before Congress can extend expiring tax cuts.

Numerous differences on other policy issues like Medicaid and welfare also are hanging up a final agreement on budget cuts, but Alaska drilling remains the biggest obstacle. It wasn't supposed to be that way when the budget process began in February.

Even though a majority in both the House and Senate support drilling in the refuge, filibuster threats by drilling opponents in the Senate have always blocked efforts to pass it as part of broader energy legislation. The filibuster threat means it effectively takes 60 votes in the 100-member Senate to pass ANWR drilling under normal rules.

To clear that hurdle this year, Senate advocates of drilling, especially Ted Stevens, R-Alaska, and Energy Committee Chairman Pete Domenici, R-N.M., put the issue on the sweeping budget measure, which cannot be filibustered.

The Arctic drilling plan is eligible for the budget because it would bring the government about $2.5 billion in revenues through oil leases through 2010, say official congressional scorekeepers. Leasing supporters say the revenues could be as high as $5 billion in that time because of high oil prices.

While use of a filibuster-proof budget bill is the only way to get the Arctic drilling plan through the Senate, it gives House GOP opponents of drilling a decisive advantage. The defection of just 14 Republicans can scuttle the entire budget bill if every Democrat votes against it. House Speaker Dennis Hastert, R-Ill., felt he had no choice but to strip drilling out of the bill last month after 25 Republicans signed a letter demanding it.

That further emboldened moderate Republicans. Now that Republican leaders are hoping to reinsert the ANWR provision into the final bill, the GOP opponents of ANWR are holding firm.

"We're assuming that ANWR will be out of the bill," said Rep. Nancy Johnson, R-Conn.

In a longshot bid to keep the drilling provision alive, Republicans are seeking out House Democrats to see if there are ways to persuade them to support the broader budget bill. The top targets are the 30 or so Democrats who support ANWR drilling as a stand-alone measure, as well as Gulf Coast lawmakers desperate for financial help for their constituents.

But there's no indication the Republicans are making headway with House Democrats, none of whom voted for the budget plan the first time around last month. They oppose the bill for cuts to Medicaid, student loan subsidies and food stamps, among other provisions. And they complain that the budget cut bill, when coupled with companion tax bills, actually leads to an increase in the deficit.

"I can't trade Medicaid cuts for being able to open up ANWR," said Rep. Gene Green, D-Texas, an oil industry supporter.

Some Democrats, however, haven't shut to the door to such overtures. Reps. Charles Melancon of Louisiana and Gene Taylor of Mississippi, for example, are demanding immediate relief for their hurricane-ravaged constituents rather than the longer-term aid being offered so far.

House Minority Leader Nancy Pelosi, D-Calif., said the GOP plan to lure Democratic votes isn't working. She said several lawmakers have "come to me and said, 'They've approached me. I want you to know I won't have anything to do with it."'