The U.S. military says three American soldiers have been killed in a bomb attack west of Baghdad.

There were also reports of Iraqi casualties from the blast, which occurred in the town of Khaldiya.

Witnesses say a large bomb exploded near a U.S. military convoy, and several vehicles were said to be on fire.

Khaldiya is in the so-called "Sunni Triangle," where attacks on coalition troops and Iraqis working with the United States are frequent. On Saturday, a car bomb killed three U.S. soldiers and wounded six at a military checkpoint in Khaldiya.

Elsewhere in Iraq, the U.S. military says three Iraqis were killed early Tuesday in a raid in the town of Beiji, north of Saddam Hussein's hometown of Tikrit.

The military says the three men were suspected members of a group known as "Mohammed's Army" that has been staging attacks on coalition forces.

Earlier Tuesday, United Nations Secretary General Kofi Annan said he will send a team to Iraq to explore the possibility of holding elections in the next few months, if he receives adequate security assurances.

Mr. Annan made the announcement in a statement released in Paris.

The United States and the U.S.-appointed Iraqi Governing Council have asked Mr. Annan to study the election issue.

Iraq's top Shiite Muslim leader, Ayatollah Ali al-Sistani, is demanding direct elections before a planned transfer of power to Iraqis from the U.S.-led coalition by the end of June. His followers have staged huge marches in support of the demand.

Both the United States and the Iraqi Council say there is not enough time to organize free and fair elections before the planned restoration of Iraqi sovereignty.

The U.S.-backed plan calls for handing over power to an interim Iraqi government chosen through regional caucuses. The interim administration is to run the country and organize general elections by the end of 2005.

The United Nations pulled its staff out of Iraq last year, following deadly attacks on its Baghdad offices that killed more than 20 people, including the top U.N. envoy to the country.

Some information for this report provided by Reuters, AFP and AP.