Donald Trump offered Japan assurances Friday that mutual defense agreements cover the disputed Senkaku Islands, claimed by China as the Diaoyus.

After repeatedly questioning defense pacts, Trump signed off on a joint statement with Prime Minister Shinzo Abe that reaffirms America's security guarantee.

The pair said they "oppose any unilateral action that seeks to undermine Japan's administration of these islands," in comments that are sure to rile Beijing.