Two U.S. warships sailed through the Taiwan Strait Monday.
The pair of US Navy warships conducted "a routine Taiwan Strait transit in accordance with global law", Pacific Fleet spokesperson Lt. j.g.
The voyage "demonstrates the USA commitment to a free and open Indo-Pacific", said Cmdr.
The warships passed through Taiwan Strait as the USA military increases the frequency of transits through the strategic waterway despite opposition from China.
Chinese security experts blasted the move by saying it suggests Washington would stand by Taiwan in case of a crisis with China.
The Arleigh Burke-class destroyer USS Curtis Wilbur and Ticonderoga-class cruiser USS Antietam traversed the strait Monday, US Pacific Fleet confirmed to Business Insider.
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It was explaining the options to migrants and helping those who chose to apply for refugee status to navigate the lengthy process. The much talked about caravan of Central American migrants has been forced to turn around at the Mexico-Guatemala border.
China expressed concerns to the US after a similar transit by two USA warships in July. The U.S. Navy has conducted such transits through the Taiwan Strait for years but have not publicized the transits since 2007.
Mattis added that "the USA will fly, sail, and operate wherever worldwide law allows, and we encourage all nations to confidently exercise their right to do the same".
China considers Taiwan a province of the mainland and officials have stated over the years that the democratic island's continued self-rule can not continue indefinitely.
Beijing has stepped up the frequency and scale of military drills around Taiwan since 2016, when the Democratic Progressive Party (DPP), a pro-independence party, won the election in Taiwan. Taiwan receives support and defense funding from the United States in line with a 1979 bilateral agreement.
It has also viewed US overtures toward Taiwan with alarm, including its unveiling a new de facto embassy in Taiwan and passage of the Taiwan Travel Act, which encourages USA officials to visit the island. China maintains Taiwan is a breakaway province and not an independent nation.
China has also alarmed Taiwan by ramping up military exercises this year, including flying bombers and other military aircraft around the island and sending its aircraft carrier through the narrow Taiwan Strait separating it from Taiwan.