Admiral Scott Swift, Commander of the U.S. Pacific Fleet, speaks at a news conference near the damaged USS John McCain and the USS America at Changi Naval Base in Singapore August 22, 2017. REUTERS/Calvin Wong

TOKYO (Reuters) - The commander of the U.S. Navy’s Pacific Fleet said on Tuesday that China’s military budget had a troubling lack of transparency, a day after Beijing announced the biggest hike in military spending in three years.

China on Monday unveiled an 8.1 percent rise in defense spending for 2018, fuelling an ambitious military modernization program and making its neighbors, particularly Japan and self-ruled Taiwan, nervous.

“These investments and commitment need to be taken with full transparency,” Admiral Scott Swift said during a press roundtable in Tokyo.

China’s “intent is not clearly understood”, he said.

China insists its military spending is transparent and that it does not pose a threat, but is needed to update old equipment and defend its legitimate interests.

China’s state media on Monday said the 2018 defense budget was proportionate and low. Chinese defense spending is only officially about one-quarter of the military spending of the United States.

But many foreign analysts and diplomats say China under-reports the figure.