Japan plans to donate more than $10 million through international organizations to Iraqi and Syrian refugees displaced by the Islamic State militant group, sources with knowledge of Japan-U.S. relations said on Tuesday.

The Abe administration sees the humanitarian aid as its contribution to the coalition the United States is forming to combat the group, the sources said.

"We plan to extend humanitarian assistance as our country is not allowed to make military contributions," Chief Cabinet Secretary Yoshihide Suga told a news conference on Tuesday.

Japan has already contributed $7.8 million in humanitarian aid to the refugees, and the United States has urged Tokyo to expand the assistance.

The government is making arrangements to pledge the additional aid on Friday at a ministerial meeting of the U.N. Security Council to discuss how best to support the Iraqi government in its fight against the Islamic State group.

With the United States building support for its plan to expand airstrikes against the militants, including those in Syria, Secretary of State John Kerry has vowed to form the widest possible coalition against the Islamic State.

An estimated 600,000 people were displaced by the Syria-based militant group in northern Iraq in August alone, the United Nations said. Three million Syrian refugees had fled to neighboring countries by the end of August, and another 6.5 million displaced residents inside Syria.