A 200-member Air Self-Defence Force transport unit has been flying C-130 planes between Kuwait and southern Iraq to support US missions there, the Yomiuri Shimbun newspaper said.
The government is considering whether to expand its mission to include flights between Kuwait and Qatar, where the US Central Command is stationed, the Yomiuri said citing informed sources.
The US has asked Japan to fly transport aircraft from Kuwait to other destinations in Iraq, including Baghdad, after the Japanese ground troops pull out, the Yomiuri said.
In response to the US request, the Japanese government has chosen missions that would pose less danger to the air unit, the Yomiuri said.
Japan has not officially decided when to pull out its ground troops.
Japan, a close ally of the United States, has some 600 ground troops on a humanitarian mission in Samawa in southern Iraq, considered a relatively safe area. The current mission expires in December but Iraq wants an extension.
It is Japan's first deployment to a country where fighting is ongoing since its World War II defeat. To avoid violating Japan's pacifist constitution, the government says the troops operate in a "non-combat zone" within Iraq.
The troops have relied on Australia and other countries for their security.