Congressional Republicans are pressing a new round of confrontation with the White House over environmental protections, adding one more large complication to the already difficult task of finishing work on the annual spending bills.

As they wade through legislation funding the operations of government, lawmakers have inserted dozens of provisions aimed at easing the regulatory burden on business, largely in the environmental arena. These include measures that would block the administration from collecting higher royalties from oil companies, allow mining companies to dump more waste on federal lands, prevent the tightening of fuel economy standards for light trucks and defund international efforts to fight ozone depletion.

In the past, the Clinton administration acquiesced to some similar proposals as the price of going along with larger legislation it wanted. But this year, it has adopted a tougher stand, signaling that the president is ready to veto major appropriations bills if lawmakers do not remove what he considers to be anti-environmental provisions.

Last week, for instance, administration lobbyists told lawmakers that President Clinton would veto the otherwise noncontroversial energy and water spending bill if it included a provision blocking efforts to toughen the current wetlands permit process. GOP lawmakers subsequently softened the language, but Democrats said they did not go far enough.

Environmentalists also are pressuring the administration to veto a bipartisan transportation appropriations bill because it would block new fuel economy standards for light trucks. Clinton allowed similar language to become law in the past, but this year Vice President Gore has indicated to environmentalists that he would raise the issue with the president.

Indeed, Gore's presidential hopes appear to be playing some role in the harder line at the White House. Gore is facing a strong challenge from former senator Bill Bradley (N.J.) for the Democratic presidential nomination, and Bradley recently was endorsed by the advocacy group Friends of the Earth.

"They're very committed, especially given the endorsement by Friends of the Earth," House Democratic Whip David E. Bonior (Mich.) said of the administration. "They're going to be looking for environmental things to be strong on, and I applaud them for it."

Since taking control of Congress after the 1994 elections, Republicans regularly have used must-pass spending bills to attack the administration's environmental policy: Congress last year passed 42 such provisions, known as "riders," and included three of them in disaster relief bills in 1999, according to the U.S. Public Interest Research Group, an advocacy organization. At least 39 riders appear on nine of the appropriations bills for the fiscal year that will begin next month, and more may be added as House and Senate members continue to hammer out the details of legislation.

"I certainly think that will be one of the most controversial aspects of our negotiations," said House Appropriations Committee Chairman C.W. Bill Young (R-Fla.), who has tried unsuccessfully to keep riders off many of the spending bills.

When Republicans assumed the majority in 1995, it was the House that moved aggressively to slash environmental regulations, in one instance attaching 17 riders to a single bill. This year the Senate has taken the lead, inserting language friendly to the oil, mining and timber industries.

"This is a classic case of nature versus nurture," said Friends of the Earth legislative director Courtney Cuff. "The Senate chose to nurture subsidies for campaign contributors at the expense of the environment."

The stricter fuel regulations, which have been blocked from taking effect for the past four years, have been the subject of a feverish lobbying battle on both sides this year. Environmentalists say the regulations proposed by the administration are an important tool in limiting air pollution, and the activists are trying derail an otherwise noncontroversial transportation measure over the issue. The Alliance of Automobile Manufacturers ran print and radio ads in nine states, including the Dakotas, Maine and Delaware, opposing the tighter rules.

"From the industry's standpoint, automakers have increased fuel efficiency dramatically, and they're working to increase it in the future," said alliance spokeswoman Gloria Bergquist. "But there are some who think we have a magic wand that we can wave over light trucks and improve their fuel efficiency automatically overnight."

When the Senate voted on a bipartisan measure that would have reinstated the standards on Sept. 15, the auto industry's presence was evident on Capitol Hill. Ford Motor Co. Chairman William Clay Ford Jr. personally appealed to Sen. Olympia J. Snowe (R-Maine), although Snowe voted in favor of the new standards.

The Senate voted once again to block the new standards, but the White House won enough votes to sustain a possible veto.

The Senate engaged in an even more protracted struggle this month over how to calculate oil royalties, a hot-button issue for environmentalists. Administration officials argue that the industry deliberately has underpaid the federal government by $66 million a year by inaccurately estimating the value of the oil it extracts from federal lands. But lawmakers from oil states have blocked new rules basing royalties on the market price of oil by including prohibitions in three spending bills over the past 18 months.

Sen. Barbara Boxer (D-Calif.) waged a filibuster on the issue, and it took Sen. Kay Bailey Hutchison (R-Tex.) two weeks to muster enough votes to reinsert language halting the royalty changes. Hutchison, calling it "one of the hardest fights I've ever had," said she and her allies were merely asserting their institutional prerogatives.

"I think it's important to take a stand that Congress should make tax policy, not federal agencies," she said.

Boxer described the oil industry's current stance as "an intentional defrauding of the United States taxpayer." She voiced hope that Clinton would be willing to make the royalties question one of his top priorities when he sits down to negotiate with Republicans this fall.

Staff writer Charles Babington contributed to this report.