HONG KONG—The U.S. plans to formally oppose a swath of Chinese territorial claims in the South China Sea, according to people familiar with the matter, as Washington takes a harder line against Beijing’s efforts to assert control over the strategic waters.

While Washington has previously said it sees Beijing’s expansive sovereignty claims over most of the South China Sea as unlawful, the State Department is preparing to issue a position paper that officially rejects specific Chinese claims for the first time, the people said.

Read More