The U.S. state of Virginia on Thursday voted to include the name of "East Sea" in its new school textbooks, leaning toward South Korea in its battle with Japan over naming of the body of water that separates them.

The House of Delegates passed the bill in a vote of 81 to 15, under which "all textbooks" approved by the Board of Education, when referring to the Sea of Japan, "shall note that it is also referred to as the East Sea."

The House and the Senate, which has approved a similar bill, will send a joint bill to Governor Terry McAuliffe for signature, who voiced his support for South Korea during his election campaign last year.

If the bill is signed into law, Virginia will become the first state in the United States to use the name of "East Sea."

Both governments of Japan and South Korea had lobbied intensely in Virginia, with Japan even threatening to suspend investment in the state in case of the bill's passage, while the state's large Korean-American population threw their weight behind South Korean government on the grounds that the name of "Sea of Japan" is a legacy of Japan's imperialistic past.

Relations between Japan and South Korea, both U.S.' treaty allies, have been strained over territorial disputes and historical issues.