Any tax imposed on financial transactions would have to take effect internationally to prevent Wall Street jobs and related business moving overseas, U.S. House Speaker Nancy Pelosi said on Thursday.

It would have to be an international rule, not just a U.S. rule, Pelosi said at a news conference. We couldn't do it alone, we'd have to do it as an international initiative.

The top Democrat's comments seemed to spell longer odds for the Wall Street tax, which some Democrats in the House of Representatives are proposing as a way to pay for job-creating legislation.

The tax, which could raise $150 billion per year, would tap into widespread public outrage at Wall Street in the wake of the financial crisis, but support is lackluster among key legislators.

This is just something that is on the table, it hasn't been developed to a high priority. but it has substantial currency in our caucus, Pelosi said.

Treasury Secretary Timothy Geithner said on Thursday that he has not seen a version of that tax that I think would be appropriate for our country.

Democrats in the House aim to pass legislation designed to create more jobs before the end of the year to ease double-digit unemployment levels that threaten an economic recovery. The Senate is expected to act early next year.

The bill could include increased road construction, money to help states avoid layoffs of police and other public employees, and a further extension of unemployment benefits, Pelosi said.

Other options include extending health-insurance subsidies for the jobless, a tax credit for businesses that create jobs, more funding for energy-efficiency programs, and low-interest loans for small businesses.

Funding for these initiatives could come from a transaction tax or by using leftover money from last year's $700 billion Troubled Asset Relief Program, a federal government program to buy assets and equity from financial institutions.

Lawmakers could also pay for the package over a five-year time period to avoid imposing tax increases or spending cuts that may hurt the nation's fragile economy.

Democrats passed a broader $787 billion stimulus bill earlier this year, but less than half of that money has been spent.

(Editing by Paul Simao)