ANKARA 

US Secretary of State Mike Pompeo voiced support for the Philippines and Vietnam on Friday over China's "highly provocative" military drills in the South China Sea.

"America agrees with our Southeast Asian friends: The PRC's [People's Republic of China] military exercise in disputed waters of the South China Sea is highly provocative," Pompeo said on Twitter. "We oppose Beijing's unlawful claims. Period."

In a subsequent tweet, he said that "in the South China Sea and elsewhere, all nations must support a free and open rules-based order that upholds the sovereign rights of all states regardless of size, power, and military capabilities."

His tweets were attached to the condemnation statements made by Philippines Cabinet Secretary Teddy Locsin and Vietnam's Press Department of Foreign Ministry.

Vietnam has defended Chinese drilling exercises between June 1 to June 5 "violated its sovereignty over the Paracel Island and it complicates the maintenance of peace, stability and cooperation in the region."

For his part, Locsin warned China if those exercises extend over Philippines territory, then they will be met with a "severe" response.

South China Sea's importance

Competing claims of territorial sovereignty over islands and smaller features in the South China Sea have been a longstanding source of tension and distrust in the region.

The sea -- a crucial passage for a significant portion of the world’s commercial shipping -- is bordered by Brunei, Cambodia, China, Indonesia, Malaysia, the Philippines, Singapore, Taiwan, Thailand and Vietnam.

Around $5.3 trillion worth of trade cruise through the South China Sea annually, with $1.2 trillion of that total accounting for trade with the U.S., said the Washington-based think tank in a report, "How Much Trade Transits the South China Sea?", published in 2017.

China claims nearly all of the 3.5-million-square-kilometer of the South China Sea, roughly 90%, and accuses US and other regional actors of violating its territorial integrity.