The USS Ronald Reagan (foreground) and the USS Nimitz Carrier Strike Groups sail together in formation in the South China Sea on July 6. China has accused the U.S. of flexing its military muscles by conducting joint exercises with two U.S. aircraft carrier groups in the strategic waterway.

The Trump administration on Monday rejected Beijing’s maritime claims in the South China Sea, wading into a conflict that has pitted China against several Southeast Asian countries with competing claims at a time of already-strained relations between Washington and Beijing.

In a statement, Secretary of State Mike Pompeo said the move was intended to strengthen U.S. policy “in a vital, contentious” region.

“We are making clear: Beijing’s claims to offshore resources across most of the South China Sea are completely unlawful, as is its campaign of bullying to control them,” Pompeo said.

China claims sovereignty over the majority of the vast and economically important Asian waterway, and in recent years has built artificial islands or expanded existing islands to bolster its claims. It has also built air strips, docks and military facilities on some South China Sea islands and asserted its broad maritime claims with coast guard ships far from Chinese shores.

Beijing’s territorial claims are depicted on Chinese maps with the so-called Nine-Dash Line, a sweeping downward arc that encompasses most of the South China Sea.

https://www.npr.org/2020/07/13/890464319/u-s-rejects-beijings-maritime-claims-in-south-china-sea