The USS Antietam, a guided missile cruiser, and the USS Curtis Wilbur, a guided missile destroyer, transited the strait Monday, sailing from south to north."USS Curtis Wilbur and USS Antietam conducted a routine Taiwan Strait Transit on October 22, in accordance with international law," Cmdr. Nate Christensen, a spokesman for US Pacific Fleet, told CNN."The ships' transit through the Taiwan Strait demonstrates the US commitment to a free and open Indo-Pacific," he added. Two US defense officials told CNN that multiple Chinese warships shadowed the two US vessels during the transit, following at a distance considered to be safe.The approximately 110-mile-wide strait separates the People's Republic of China and Taiwan and is seen as a potential geopolitical flashpoint should Beijing ever seek to take the island of Taiwan by force.Beijing continues to lay claim to Taiwan, a self-governed, democratic island, which it views as a breakaway province.While the strait constitutes international waters, China is thought to be very sensitive about the presence of US military forces in the strait, and in recent years, the US has only sailed warships through the waterway about once a year. The US Navy has not sailed an aircraft carrier in that area since 2007.However, the frequency of those transits has increased this year, with the US also sailing two destroyers through the Taiwan Strait in July.Chinese Foreign Ministry spokeswoman Hua Chunying told journalists Tuesday that China had already expressed "serious concern" to the United States following the transit."We urge the US to stick to the one China principle … and cautiously and appropriately handle the Taiwan issue to avoid harming Sino-US ties, and peace and stability in the Taiwan strait," she said.Despite the lack of formal diplomatic ties, Taiwan remains an important American ally in the region, and the Trump administration has sought closer ties between Washington and Taipei.America's alliance with Taiwan has long been lambasted by officials in Beijing.The Chinese military conducted large-scale military exercises in the Taiwan Strait in April, drills that analysts saw as a warning over growing ties between the US and Taiwan.The issue of Taiwan was raised in a recent meeting between US Secretary of Defense James Mattis and his Chinese counterpart, Gen. Wei Fenghe, which took place Thursday on the sidelines of the ASEAN-led forum in Singapore."Minister Wei raised Taiwan concerns about our policy," US Assistant Secretary of Defense for Asian and Pacific Security Affairs Randall Schriver told reporters traveling with Mattis.Mattis "reassured Minister Wei that we haven't changed our Taiwan policy, our one China policy," Schriver added, saying that on issues like Taiwan and the South China Sea, "we're going to continue to have differences."A previously planned meeting in Beijing between the two defense chiefs was called off late last month amid US-China tensions surrounding the Trump administration's sanctioning of Beijing over its purchase of Russian weapons systems.The US has ramped up its criticism of China's militarization of islands in the South China Sea."China's militarization of the South China Sea and aggressive action in international waters destabilizes the region and threatens shared efforts to promote security," Mattis said at the ASEAN-US meeting following his meeting with Wei. "The US will fly, sail, and operate wherever international law allows, and we encourage all nations to confidently exercise their right to do the same," Mattis added.US defense officials previously told CNN that the US military was weighing a major show of force to demonstrate the US is prepared to deter and counter Chinese military actions. Last week, the US flew B-52 bombers near the contested Spratly Islands in the South China Sea, and last month, the US Navy destroyer USS Decatur sailed within 12 miles of two of the Spratly Islands as part of what the US calls a "freedom of navigation operation."During that operation, a Chinese destroyer came within 45 yards of the US warship, forcing it to maneuver to avoid a collision.The US labeled the Chinese warship's actions unsafe and unprofessional while Beijing said the US was threatening the safety and sovereignty of China.