A US-made 70-C helicopter lands on a Perry-class frigate during the Han Kuang drill on the sea near eastern Hualien on September 17, 2014. Taiwanese navy fired rockets and guns on September 17 in a scenario simulating a Chinese invasion in the island's biggest live-fire naval drill in 25 years.

The United States is considering a new operation to send warships through the Taiwan Strait, U.S. officials tell Reuters, a mission aimed at ensuring free passage through the strategic waterway but which risks heightening tensions with China.

The U.S. Navy conducted a similar mission in the strait's international waters in July and any repeat would be seen in self-ruled Taiwan as a fresh expression of support by President Donald Trump's government.

The U.S. military declined comment and U.S. officials who discussed the deliberations, which have not been previously reported, did so on condition of anonymity. They did not discuss the potential timing for any fresh passage through the strait.

China views Taiwan as a wayward province and has been ramping up pressure to assert its sovereignty over the island. It raised concerns over U.S. policy toward Taiwan in talks this week with U.S. Defense Secretary Jim Mattis in Singapore.

Even as Washington mulls ordering a fresh passage through the strait, it has been trying to explain to Beijing that its policies toward Taiwan are unchanged. Mattis delivered that message to China's Defense Minister Wei Fenghe personally on Thursday, on the sidelines of an Asian security forum.

"Minister Wei raised Taiwan and concerns about our policy. The Secretary reassured Minister Wei that we haven't changed our Taiwan policy, our one China policy," said Randall Schriver, a U.S. assistant secretary of defense who helps guide Pentagon policy in Asia.

"So it was, I think, a familiar exchange."

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. The Pentagon says Washington has sold Taiwan more than $15 billion in weaponry since 2010.