This summer, Beijing and Washington began publicly airing conflicting viewpoints on the status of the waters, over which the former claims jurisdiction, but which the latter argues grants foreign commercial and military vessels a right to unimpeded use. The legal basis for China’s position revolves around its claim to Taiwan itself, which neither the United States nor Canada officially recognizes.

The U.S. sails naval assets through the strait on a near-monthly basis to assert navigational rights. In September, a frigate from the Royal Canadian Navy and a U.S. Navy destroyer conducted their only joint transit of the year so far. Melanie Joly, Canada’s foreign minister, has promised more of the same.

“We have made it clear on multiple occasions that China has sovereignty, sovereign rights and jurisdiction in the Taiwan Strait,” China’s foreign ministry spokesperson Mao Ning told a regular briefing on Monday.

“China always respects the navigational rights that countries are entitled to in accordance with international law. However, we firmly reject any country’s provocation and threat against China’s sovereignty and security in the name of freedom of navigation,” said Mao.

The U.N. Convention on the Law of the Sea, which China has ratified, but the U.S. hasn’t, grants coastal states a 12-nautical mile territorial sea, the use of which by foreign vessels is at the state’s discretion. Beyond that zone, however, vessels have a right to navigate the “high seas,” commonly called international waters, including through straits.

This right technically wouldn’t apply if Taiwan were recognized as part of Chinese territory. But when Washington established diplomatic ties with Beijing in 1979, it acknowledged, rather than recognized, Chinese claims to the island. When Ottawa did the same in 1970, it similarly took note, rather than endorsed, Beijing’s claim.

U.S. Navy warships that transit the Taiwan Strait emphasize their use of “a corridor in the strait that is beyond the territorial sea of any coastal state.”

“The United States will continue to fly, sail and operate wherever international law allows, and that includes transiting through the Taiwan Strait,” a U.S. government spokesperson told Newsweek in June.

Joly told the Financial Times that Western allies needed to ensure the waterway “remains an international strait.” The passage sits at the northeastern mouth of the South China Sea, which the U.N. estimates hosts one-third of global maritime trade. Some 40 percent of the EU’s trade goes through the strait, the bloc’s foreign affairs chief, Josep Borrell, said recently.

“We will continue to enforce the international rules-based order when it comes to the Taiwan Strait. And that’s why also we had a frigate going through the Taiwan Strait this summer, along with the Americans, [and] we’re looking to have more frigates going through it,” Joly was quoted as saying in the FT on Monday.

Ottawa has military assets in East Asia as part of its contribution to enforcing U.N. Security Council sanctions on North Korea. Canadian air force pilots also have had a number of well-documented run-ins with their Chinese counterparts in the East China Sea.

Canada’s Indo-Pacific strategy, announced last week, promised further engagement on security matters in the region. Joly said Canada would increase its warship presence from one to three, while also posting more diplomats and military attachés throughout the region. She also previewed more investment in the Five Eyes intelligence-sharing alliance with the U.S., the U.K., Australia and New Zealand.

“We know we have to do more to play a role in the security of the region,” Joly said. “We need to invest in deterrence because we believe . . . it is the best way to, at the end of the day, respect international norms,” the paper quoted her as saying.

Separately, the Pentagon also released its annual China Military Power Report last week. The document said Beijing was likely to continue military, diplomatic, information and economic pressure on Taiwan to compel the island’s unification with China. Taipei rejects Beijing’s sovereignty claims.

The report also projected that China’s nuclear stockpile could grow to 1,500 warheads by 2035 if it continued its current rate of expansion.

Do you have a tip on a world news story that Newsweek should be covering? Do you have a question about cross-strait relations? Let us know via worldnews@newsweek.com.