UPDATE 3-Senate Republicans adopt voluntary earmark ban

* Reid says will schedule vote for a binding ban

* Few Democratic senators support ban

* Earmarks account for less than 0.5 percent of spending (New throughout with Republican voluntary ban)

WASHINGTON, Nov 16 (Reuters) - Republicans in the U.S. Senate on Tuesday adopted a voluntary ban on the congressional pet projects known as earmarks, and the chamber’s Democratic leader said he would allow a vote on a binding moratorium.

Republicans in both the Senate and the House of Representatives have now forsworn earmarks as they eye large spending cuts in the coming year, when they will control the House and wield greater influence in the Senate.

Though earmarks account for less than one half of a percent of the federal budget, they have become a symbol of wasteful spending for many grassroots Tea Party activists who helped Republicans win big in the Nov. 2 elections.

“I think it shows that this conference is serious about doing what it said we were going to be about -- limited government, spending reduction, dealing with the national debt,” said newly elected Republican Senator Marco Rubio.

Senate Majority Harry Reid said he would allow a vote on a binding, two-year ban that would apply to everyone in the Senate, though only two of the chamber’s 59 Democrats have said they support the measure.

“I would be happy to work, to set up a reasonable time to have a debate on that and have a vote on it,” Reid told a news conference.

Earmarks, which have accounted for roughly $16 billion of the $3.5 trillion federal budget in recent years, have been a popular way for lawmakers to steer federal dollars back to their home districts and states.

Reid, who represents Nevada, and other backers also say they are a way to ensure that Congress maintains some control over federal spending that otherwise would be managed by government agencies.

A ban would not necessarily save money, they say.

“I think I have an obligation to the people of Nevada to do what’s important to Nevada and not what’s important to some bureaucrat with green eyeshades,” Reid said.

Democrats have sought to rein in earmarks in recent years after they factored in several corruption scandals, though they have not backed an outright ban.

An earmark ban could worsen congressional gridlock as they often serve as sweeteners to build support for the large spending bills that are needed to keep the government running, said Thomas Stratmann, an economics professor at George Mason University.

“To the extent that earmarks grease the wheel they are beneficial,” Stratmann said.

In the Senate, two Democrats have joined several Republicans to press for a vote on an earmark ban as soon as Wednesday, though Reid indicated he might not let that happen so soon.

“It’s not clear to me if or when we’ll get a vote on earmarking,” said Democratic Senator Claire McCaskill, who supports the ban. “I think it depends on how far the Republican caucus is willing to go to force a vote on it.”

In the House, Republicans adopted a voluntary ban earlier this year and are expected to schedule a vote for a binding ban soon after they take control in January.

Additional reporting by Richard Cowan; Editing by Eric Walsh and Cynthia Osterman