By Andrea Shalal-Esa

WASHINGTON, Oct 14 (Reuters) - President George W. Bush must seek congressional approval before taking any military action in Iran, unless Tehran attacks the United States first, House Speaker Nancy Pelosi said on Sunday.

"We don't believe that any authorities that the president has would give him the ability to go in without an act of Congress," Pelosi told ABC's "This Week" program.

"Any president, if we are attacked, if our country is attacked has -- even under the War Powers Act -- very strong powers to go after that country. But short of that, he must come to the Congress," said the top Democrat in the House of Representatives.

Pelosi said Bush had not requested any congressional authority to take military action in Iran, despite growing U.S. concern over Iran's nuclear ambitions and its support for militant groups in Lebanon and Gaza.

Republican presidential candidates last week said it may be necessary to attack Iran's nuclear facilities to prevent it from developing a bomb, but they were cautious about a preemptive strike, saying Congress should be consulted first.

Iran denies trying to build a nuclear weapon, but the United States, France, Britain and other countries fear Iran's stated pursuit of nuclear-generated electricity is a precursor to learning how to build atom bombs.

Bush this month said the United States was working to resolve the nuclear standoff with Iran diplomatically but was keeping all its options open.

U.S. Secretary of State Condoleezza Rice last week said Washington was considering sanctions against the the Qods force, the elite unit of Iran's Revolutionary Guard, which it accuses of inciting violence against U.S. troops in Iraq.

The Senate last month passed a resolution urging the Bush administration to "combat, contain, and roll back" Iran's "violent activities and destabilizing influence inside Iraq," and to designate the entire Guard a "terrorist" organization.

The House passed a similar measure, but it told the White House to determine if the Guard should be labeled as such.

Iran condemned the congressional resolutions, saying any U.S. move to brand the Guard a terrorist group would amount to a confrontation with the entire Islamic Republic.

"Whatever Iran's impact is on our troops in Iraq should be dealt with in Iraq," Pelosi said.

AlertNet news is provided by