May 8 (UPI) -- The USS Montgomery and the USNS Cesar Chavez sailed into the South China Sea this week in support of the West Capella drill ship, U.S. Indo-Pacific Command announced Friday.
Earlier this week the Air Force and Marines conducted training exercises near China amid increased tensions in the region, which is the site of competing maritime claims.
Thursday's transit, officials said, was a reaction to Chinese harassment of the drill ship in waters the Chinese government has claimed but which the United States considers international waters.
Last week the Chinese military expelled the guided-missile destroyer USS Barry from the Paracel Island chain in the South China Sea, saying the United States was intruding into Chinese waters without permission.
The West Capella is owned by Patronas, a Malaysian oil and gas company and is registered in Panama.
Adm. John Aquilino, commander of the U.S. Pacific Fleet, said U.S. forces would stand with regional friends and partners to resist coercion and oppose unlawful claims to international waters and resources.
"We are committed to a rules-based order in the South China Sea and we will continue to champion freedom of the seas and the rule of law," said Adm. John Aquilino, commander of the U.S. Pacific Fleet. "The Chinese Communist Party must end its pattern of bullying Southeast Asians out of offshore oil, gas, and fisheries. Millions of people in the region depend on those resources for their livelihood."
Both ships were already underway in the region, with Montgomery on a rotational deployment to the U.S. 7th Fleet area of operations and Cesar Chavez delivering supplies, fuel, cargo and equipment to warfighters throughout the region.