UPDATE 2-Wall St tax has "great deal of merit" - Pelosi

* Comments suggest tax could end up in House jobs package

* Tax faces resistance in Senate, White House

* Lawmakers vent anger at Wall Street (New throughout, adds byline)

By Andy Sullivan

WASHINGTON, Dec 3 (Reuters) - A proposed tax on financial transactions "has a great deal of merit" and would help raise much-needed revenue for the U.S. government, House of Representatives Speaker Nancy Pelosi said on Thursday as other backers touted it as a measure to slash Wall Street salaries.

"It is really a source of revenue that has really minimal impact on the transaction but a tremendous impact on helping us meet our needs," Pelosi said at a news conference.

Her comments suggested the proposal may find its way into a House bill aimed at bringing down the double-digit U.S. unemployment rate before the November 2010 congressional elections.

But analysts said it still faces long odds due to opposition from prominent lawmakers and the Obama administration.

Other backers tapped into widespread anger at banks like Goldman Sachs Group (GS.N) that are posting healthy profits after benefiting from a $700 billion federal bailout.

"Maybe next year they won't be able to afford $17 billion or $20 billion in bonuses because they'll have to pay a modest tax on their high-volume trading," said Democratic Representative Peter DeFazio. "Maybe the average salary will drop to four or five hundred thousand (dollars). Heavens."

DeFazio's measure would apply to trades made by U.S. businesses or residents, no matter where they take place.

It would tax futures contracts, swaps and credit default swaps at a rate of 0.02 percent and stock transactions at 0.25 percent. Options would be taxed at the rate of the underlying asset.

The tax would be refunded for mutual funds and savings accounts for retirement, education and healthcare. It would not apply to the first $100,000 of activity.

The G20 group of industrialized countries asked the International Monetary Fund last month to consider a "Tobin tax" or other methods to fund bank bailouts. The concept is named for economist James Tobin, who proposed a similar measure in the 1970s to dampen foreign exchange trading.

But the envisioned $150 billion per year that would be raised by DeFazio's proposal would not go to Wall Street.

The money would be used to reduce the federal deficit and fund new construction projects and other measures aimed at bringing down the unemployment rate -- now at 10.2 percent -- as the United States struggles to emerge from recession.

LONG ODDS IN SENATE

Even if the tax is included in the House's jobs bill, Wall Street allies like Democratic Senator Charles Schumer will be able to block it in the Senate, Concept Capital tax analyst Anne Mathias said.

So far, Democrat Tom Harkin and Independent Bernie Sanders are the only lawmakers to back it in the Senate.

Pelosi and other lawmakers have said the bill would have to apply internationally to ensure that financial activity does not move overseas.

Another bill crafted by Representative John Larson, the No. 4 Democrat in the House, would rope in international bodies like the World Trade Organization to ensure compliance.

Britain, France and several other countries already apply a tax on financial transactions, and the United States had one in place from 1914 to 1966.

"There's pretty much consensus around the world that derivatives are not a good thing," DeFazio said, referring to the complex bets that brought down firms like American International Group (AIG.N).

A left-leaning group, the Center for Economic and Policy Research, released a letter of support signed by more than 200 economists. Labor groups like the AFL-CIO back the measure as well, while business groups like the U.S. Chamber of Commerce oppose it.

Anger has been growing among rank-and-file Democrats who say the Obama administration has worried too much about Wall Street and not paid enough attention to the struggles of ordinary Americans.

On Wednesday, black Democrats boycotted a House committee vote on financial services regulation, saying the administration needed to pay more attention to less affluent Americans who have borne the brunt of the recession.

Obama on Thursday hosted a forum with business and labor leaders at the White House to discuss how to boost jobs. (Additional reporting by Thomas Ferraro; Editing by John O'Callaghan) ((andy.sullivan@thomsonreuters.com; +1 202 898 8391; Reuters Messaging: andy.sullivan.reuters.com@reuters.net))