Taipei, Taiwan - Two US Navy warships sailed southward through the strategic Taiwan Strait for the first time since a visit by US House Speaker Nancy Pelosi that was harshly condemned by China.

The guided-missile cruisers USS Antietam and USS Chancellorsville were on a "routine" mission through international waters, the US Navy's 7th Fleet said in a statement on Sunday.

"The ship's transit through the Taiwan Strait demonstrates the United States' commitment to a free and open Indo-Pacific. The United States military flies, sails, and operates anywhere international law allows," the statement said.

Taiwan's Defense Ministry said it was closely monitoring the two ships.

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The action marks the first passage of US warships since a visit in early August by Pelosi, who led a congressional delegation to the self-ruled island democracy.

The brief visit, during which Pelosi pledged Washington's solidarity, drew the ire of the leadership in Beijing.

In response, the Chinese military held large-scale maneuvers around Taiwan.

On Friday, Taiwan's foreign minister, Joseph Wu, said China's decision to conduct military drills near Taiwan was an attempt to stop the Taiwan Strait from being used as international waters.

"That kind of exercises is trampling on the status quo," Wu said.

Taiwan has had an independent government since 1949, but China considers the democratic island part of its territory and opposes any form of official contacts between Taiwan and others.

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Wang Ting-yu, a lawmaker of Taiwan's ruling Democratic Progressive Party in the parliament's Foreign and National Defense Committee, on Sunday showed photos of US warships sailing through the strait on his Facebook page, writing the waterway is by no means China's inland sea.

"The international community defends the international order and will never allow an international trouble-maker to behave unscrupulously," Wang said.

In August, Chinese fighter jets and warships operated intensively in the 81-mile-wide Taiwan Strait. Some warplanes repeatedly crossed the median line, which Taiwan views as a political boundary marking its area of control and which China has generally respected in the past.