Conservative leaders are confident that their opposition to higher taxes scuttles any chance that President Bush will make a deal with congressional Democrats to overhaul Social Security.

“Nothing will happen in the next two years” on Social Security, said Grover Norquist, president of Americans for Tax Reform. After lobbying Mr. Bush and Treasury Secretary Henry Mr. Paulson, Mr. Norquist said the officials made clear to him that “they don’t intend to raise taxes.” Some Democrats have made Mr. Bush’s willingness to consider tax increases a precondition for negotiations over Social Security.

Mr. Norquist and representatives of three other anti-tax organizations gathered on Capitol Hill in Washington on Tuesday to demonstrate opposition to any deal that fixes Social Security by lifting payroll taxes. Intending to buttress Mr. Bush’s opposition to higher levies, the groups ruled out steps that Democrats say are critical to ensuring the program’s solvency.

Social Security instead requires a complete transformation, conservatives asserted at the conference organized by the Free Enterprise Fund, Institute for Policy Innovation, National Taxpayers Union and Americans for Tax Reform.

The program can’t be restructured by tinkering with benefits or revenue and needs an overhaul that includes private accounts controlled by individuals, the groups argue.

Opposition by Democrats, who now control Congress, to such accounts, coupled with Republican resistance to new taxes, makes any alteration to the federal pension system while Mr. Bush is in office unlikely. His term ends in January 2009.

Mr. Bush and a former treasury secretary, John Snow, campaigned across the nation for partial privatization of Social Security in 2005, shelving the idea after encountering widespread opposition.

“If either side starts sensing that there’s a political advantage in playing the issue for the 2008 elections, then it’s hopeless,” Mr. Snow, now the chairman of New York-based Cerberus Capital Management LP, said in an interview Tuesday in London. “Each side must put down their swords and get an agreement by following facts.”

Mr. Paulson, who has made changes to Social Security his main domestic objective, has adopted a more nuanced approach than his predecessor. He has repeatedly stressed openness to discussing all options. That’s giving some Democrats hope that a deal can be struck.

“If they will take these private accounts off the table, then there is a possibility of moving ahead,” Rep. Collin Peterson, a Democrat of Minnesota and chairman of the House Agriculture Committee, said in an interview in Washington.

Social Security and Medicare, known as entitlement programs, threaten to dominate the federal budget in a generation. The cost of Social Security is forecast to jump as much as 80% to $789 billion from 2005 to 2015.

Mr. Paulson, 60, a former Goldman Sachs Group Inc. chief executive officer, has reached out to Democrats since taking office in July. He stayed out of the November elections, giving him more credibility with opposition lawmakers willing to consider a deal on Social Security. Mr. Paulson and Treasury spokeswoman Brookly McLaughlin declined to comment.

Tim Penny, a former Democratic congressman from Minnesota, said an agreement on Social Security is possible this year because Mr. Paulson is untainted by the partisan battles of previous years and some Democrats want to come up with a solution.

“That there is discussion on how Social Security could be put back on the table, it’s encouraging,” said Ms. Penny, now a senior fellow at the Hubert H. Humphrey Institute of Public Affairs at the University of Minnesota in Minneapolis. “Democrats now have a fair amount of control of the final product,” making them more likely to pursue a deal than when Republicans ran Congress, he added.

Norman Ornstein, a fellow at the Washington-based American Enterprise Institute, said the opposition of conservatives to tax increases would make it extremely difficult for Mr. Bush to strike a compromise with Democrats on Social Security.