The U.S. Senate has unanimously approved an amendment that reaffirms Washington's commitment to Japan in its territorial dispute with China over islands in the East China Sea.

The measure was attached Thursday to the National Defense Authorization Bill for Fiscal Year 2012, which is still being debated in the Senate – the upper body of Congress.

The amendment says that the U.S. acknowledges Japan's administration over the Senkaku islands, but does not take a position on the ultimate sovereignty of the territory. It also notes U.S. opposition to any efforts to coerce, threaten or use force to resolve the territorial dispute.

The resource-rich islands are known as the Daioyu Islands in China.

U.S. President Barack Obama is expected to sign the defense bill after it passes the House of Representatives.