Japan is worried Thursday's mortar attack at Baghdad International Airport could hinder the start of Air Self-Defense Force (ASDF) airlift operations for Iraq reconstruction, Defense Agency chief Shigeru Ishiba said Friday.

"We will closely examine the situation as it could affect ASDF activities," Ishiba told reporters. Tokyo will ask relevant countries to investigate the situation as it has no means to do so itself, Ishiba added.

The Japanese government envisages ASDF airplanes using the airport to help US-led coalition forces.

It is difficult for Japan to immediately judge if the envisaged ASDF operation will be feasible at the airport, Japan's Chief Cabinet Secretary Yasuo Fukuda said at a separate news conference.

One US soldier was killed and another was wounded in a mortar attack on US military installations near Baghdad airport Thursday, according to Kyodo News.

Kyodo quoted a US Army spokesman as saying about four mortar rounds struck a logistics base near the airport and the airport complex itself, which lies a few kilometers west of Baghdad and is a key command center for US military operations in Iraq.

Japan has deployed a 200-strong ASDF contingent to airlift relief goods and supplies for the US-led coalition forces, using three C-130 cargo planes based in Kuwait.

Undergoing training in Kuwait, the unit is awaiting Ishiba's go- ahead for the start of the operation.

Under a special law enacted in July, Japan is sending Self- Defense Forces contingents to provide humanitarian and reconstruction assistance in areas the government calls "noncombat zones" in Iraq.