WASHINGTON, Sept 27 (Reuters) - Democrats in the U.S. House of Representatives are pushing for a new Wall Street tax that would cover the potential costs of a $700 billion bailout being negotiated by Congress and the Bush administration.

U.S. House Speaker Nancy Pelosi, speaking to reporters after a meeting with fellow Democrats, said the fee could be assessed after five years if the non-partisan Congressional Budget Office determined taxpayers had lost money in the bailout.

“If after five years ... the CBO decides that the American taxpayer has lost money in this, then there would be a fee on financial institutions,” Pelosi said, adding that she hoped the provision could be part of a final bailout deal.

Pelosi said that the Secretary of the Treasury could determine how to assess the fee.