A majority of Americans favor sending U.S. troops to invade Iraq and topple Iraqi President Saddam Hussein but want President Bush to obtain authorization from Congress before taking military action, according to a new Washington Post-ABC News poll.

The survey also found that public support for a ground war could fall dramatically if such an action produced large numbers of U.S. casualties.

As debates about Iraq rage in Washington, the poll found that an overwhelming majority of Americans agree with Bush that Hussein poses a clear danger to the United States. Most also favor taking some kind of military action to force him from power.

Nearly six in 10 57 percent said they supported a U.S. invasion of Iraq with ground troops, while 36 percent opposed such an action. When asked whether they would favor a ground war if it were to produce “significant” U.S. casualties, support plummeted to 40 percent and opposition rose to 51 percent.

The survey found a gender gap on the question of whether to send ground troops to Iraq. Men favored the action by more than two to one. Women were split, with 49 percent in favor and 40 percent opposed.

Three in four Americans view Iraq as a threat to the United States, the poll found.

A total of 1,023 randomly selected adults were interviewed Aug. 7-11. The margin of sampling error for the overall results is plus or minus 3 percentage points.