Defence chief Fukushiro Nukaga left Tokyo on Friday for an unspecified destination. Defence Agency officials said they could not comment on reports that he would visit Iraq, citing security concerns.
However, Foreign Minister Taro Aso, currently in Washington, confirmed that Nukaga would visit Iraq, Kyodo News agency reported on Saturday.
Japanese media reports also said Nukaga would arrive in Iraq as early as Saturday to visit the 600 Japanese soldiers based in the southern city of Samawa, where they are rebuilding schools, purifying water and conducting other humanitarian work.
Japan's pacifist constitution bans the use of force in resolving international disputes.
Nukaga's visit to the troops and to areas around Samawa to check safety conditions is intended to gain public support for an extension of the unpopular mission, due to expire on 14 December, Mainichi newspaper reported.
Increasingly unpopular mission
Tokyo has not announced whether the mission will be extended.
The mission, Japan's largest overseas military dispatch since the second world war has grown increasingly unpopular with the public. Many Japanese say the deployment violates the constitution and has made Japan a target for terrorism.
Iraqi Prime Minister Ibrahim al-Jaafari is to visit Tokyo on Monday for talks with his counterpart, Junichiro Koizumi, on Japan's support for Iraq's reconstruction and the role of Japanese troops in Samawa, the Iraqi Foreign Ministry said earlier.
Foreign Minister Hohshyar Zebari had earlier visited Japan to urge it to extend its deployment.
Last December, the then-Defence Agency chief Yoshinori Ono had briefly inspected Samawa and said the area was safe enough for Japanese troops to operate before an earlier one-year extension of the mission.