WASHINGTON (Reuters) - President Bush sought to reassure Americans on Saturday that the U.S.-led invasion of Iraq was appropriate despite the failure to find weapons of mass destruction and with U.S. troops under daily guerrilla attack.

Bush used his weekly radio address to echo some of the themes of his Tuesday speech to the U.N. General Assembly, where he got a cool reception from many foreign leaders who disapproved of the U.S. policy of taking pre-emptive action against countries deemed to be a threat to the United States.

"The world is safer today because, in Iraq, our coalition ended a regime that cultivated ties to terror while it built weapons of mass destruction," Bush said.

The U.S. president was ending a tough week. At the United Nations, some foreign leaders voiced skepticism over his appeal for help to rebuild Iraq.

In a blow to hopes that his pre-war claim that Iraq possessed weapons of mass destruction, U.S. officials revealed that an interim report on Iraq's weapons was expected to say no conclusive evidence of such weapons have yet been found.

At home, members of Congress raised concerns about his $87 billion proposal for Iraq, forcing the White House to defend spending items like a $54 million computer study for Iraq's postal service.

A poll released on Saturday showed more than half of voters surveyed thought America was spending too much money in Iraq, and almost three quarters favored turning over some authority to the United Nations to get other countries to help out.

Concerns over the direction of policy in Iraq, as well as the sputtering U.S. economy, have also hit Bush's own approval ratings. Only 46 percent of registered voters surveyed for the Newsweek poll said they would like to see Bush re-elected, while 47 percent said they would not.

The White House is still hoping to draw more international support for Iraq.

"I am confident that more nations will rally to the side of the Iraqi people and help them to build a free and peaceful nation," Bush said.

The White House is reworking draft proposals that would give U.N. authorization to a multinational force under U.S. leadership to get more troops and money into Iraq. An early draft asks the unelected Iraqi Governing Council to draw up a schedule for a new constitution and elections, in cooperation with the U.S.-led occupying coalition.

France wants a rapid transfer of Iraqi self-rule from U.S. control, but Washington wants to take the time to make sure Iraq has functioning institutions.