"Thinking something out loud is not treason," Norquist, the president of Americans for Tax Reform, told Reuters in an interview.

Senators Bob Corker of Tennessee and Saxby Chambliss of Georgia, and Representative Tom Cole of Oklahoma are among a handful of Republicans openly weighing President Barack Obama's proposal to raise tax rates on household incomes above $250,000, the stickiest point in the talks to avert the "fiscal cliff."

"Right now, he has had impure thoughts on tax increases," Norquist said of the recent comments by Chambliss. "But nobody has voted for a tax increase."

Obama and U.S. House of Representatives Speaker John Boehner met on Sunday in negotiations on a potential deal, about three weeks before some $600 billion in tax increases and spending cuts begin to kick in, possibly igniting another recession.

Asked about Republicans giving in on taxes, Norquist said: "It may be unhelpful, it may be throwing marbles at Boehner's feet, but I think they are trying to be helpful."

Norquist's famed "Taxpayer Protection Pledge," signed by nearly every Republican lawmaker in the House and Senate, holds that they not raise taxes. Support has appeared to wane amid a drive to reduce deficits topping $1 trillion and with pressure from the latest fiscal standoff.

Lawmakers who sign the pledge vow to oppose any efforts to boost marginal individual and corporate income tax rates and to "oppose any net reduction or elimination of deductions and credits, unless matched dollar for dollar by further reducing tax rates."