Japan dispatched its first military unit for a humanitarian mission to Iraq on Friday, spearheading the country's biggest overseas deployment since World War II, media reports said.

The advance air force contingent of more than 40 personnel was expected to split up and take commercial flights to Kuwait from Tokyo international airport.

Kyodo News agency and NHK television said the first flight carrying some of the personnel left Friday morning. At least one other flight was expected to leave later in the day. A Defense Agency spokesman declined to offer details, citing security concerns.

The air force units will assess security and make arrangements for a larger 276-member air force contingent charged with shipping medical and food supplies from Kuwait to Iraq. In addition, more than 500 Japanese ground troops will be deployed in southern Iraq in February and March.

The contingent sent Friday was part of a total dispatch of about 1,000 personnel, including land, air and sea forces, on a mission to help restore water services, offer medical aid and rebuild schools and other infrastructure.

The deployment has raised opposition in Japan, where many are wary of possible casualties in Iraq and terror attacks at home. But Prime Minister Junichiro Koizumi's (search) government has stressed Japan's responsibility to help U.S.-led coalition forces restore stability to Iraq.

The government has also been keen to avoid the kind of criticism from Washington that Japan received during the first Gulf War (search) in the early 1990s, when Tokyo sent money, but no personnel.

"We want the military to make big contributions to Iraqi reconstruction and humanitarian assistance. We expect them to fulfill their duties and make major contributions," Chief Cabinet Secretary Yasuo Fukuda told a news conference Friday.

The Defense Agency plans to deploy armored vehicles and up to six naval ships, including destroyers, to support its units. Eight aircraft, including three C130 transport planes (search), will also be dispatched.

Japan also has offered the second-largest pledge for Iraqi reconstruction after the United States, promising $1.5 billion in grants for 2004 and $3.5 billion in loans for 2005-07.

The deployment will be a milestone for Japan's military, which is strictly limited by the country's pacifist constitution.