UPDATE 1-Taiwan says two U.S. warships pass through Taiwan Strait

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TAIPEI, July 7 (Reuters) - Two U.S. warships passed through the Taiwan Strait on Saturday on a voyage that will likely be viewed in the self-ruled island as a sign of support by President Donald Trump amid heightened tension with China.

Taiwan's Defense Ministry said the ships were moving in a northeastern direction, adding that the situation was in accordance with regulations.

Washington has no formal ties with Taiwan but is bound by law to help it defend itself and is the island's main source of arms. China regularly says Taiwan is the most sensitive issue in its ties with the United States.

The U.S. military declined to comment. U.S. officials told Reuters a Strait passage had been planned but declined to elaborate on the timing of such an operation, which would be the first by a U.S. Navy ship in about a year.

The mission follows a series of Chinese military drills around the island that have stoked tensions between Taipei and Beijing.

China claims Taiwan as its own and has never renounced the use of force to bring under its control what it sees as a wayward province. Taiwan has shown no interest in being governed by the ruling Communist Party in Beijing.

The move comes as a U.S.-China trade fight is seen as dragging on for a potentially prolonged period, as the world's two biggest economies flex their muscles with no sign of negotiations to ease tensions.

Friday marked the start of the U.S. duties that were promptly met with retribution by China, as Beijing accused the United States of triggering the "largest-scale trade war."

Reuters first reported last month that the United States was considering sending a warship and had examined plans for an aircraft carrier passage, but ultimately did not pursue that option perhaps because of concerns about upsetting China.

The last time a U.S. aircraft carrier transited the Taiwan Strait was in 2007, during the administration of George W. Bush, and some U.S. military officials believe a carrier transit is overdue.

U.S. overtures towards Taiwan, from unveiling a new de facto embassy to passing the Taiwan Travel Act, which encourages U.S. officials to visit, have further escalated tension between Beijing and Taipei.

China has alarmed Taiwan by ramping up military exercises this year, including flying bombers and other military aircraft around the island and sending its carrier through the narrow Taiwan Strait separating it from Taiwan.

In recent months, China's air force has held military maneuvers near the island, which Taipei has called intimidation.

China's hostility toward Taiwan has grown since Tsai Ing-wen from the pro-independence Democratic Progressive Party won presidential elections on the island in 2016. (Reporting By Jess Macy Yu; Additional reporting by Idrees Ali in Washington; Writing by Anne Marie Roantree Editing by Peter Graff and Helen Popper)