A Chinese H-6 strategic bomber flew around the Spratly Islands at the weekend in a new show of force in the contested South China Sea, a U.S. official said on Tuesday.
It was the second such flight by a Chinese bomber in the South China Sea this year. The first was on Jan. 1, said the official, who spoke on condition of anonymity.
The flight could be seen as a show of "strategic force" by the Chinese, the official said.
It comes after U.S. President-elect Donald Trump has signaled a tougher approach to China when he takes office on Jan. 20, with tweets criticizing Beijing for its trade practices and accusing it of failing to help rein in nuclear-armed North Korea.
Commander Gary Ross, a Pentagon spokesman, said he had no specific comment on China's recent bomber activities, but added: "we continue to observe a range of ongoing Chinese military activity in the region."
In December, China flew an H-6 bomber along the "nine-dash line" it uses to map its claim to nearly all of the South China Sea, a strategic global trade route. That flight also went around Taiwan, which China views as a renegade province.
In August, China conducted "combat patrols" near contested islands in the South China Sea.
Trump has enraged Beijing by breaking with decades of U.S. policy and speaking to the Taiwanese president by telephone.
A state-run Chinese newspaper warned Donald Trump on Sunday that China would "take revenge" if he reneged on the U.S. one-China policy, only hours after Taiwan's president made a controversial stopover in Houston.
Last week China said that a group of Chinese warships led by its sole aircraft carrier was testing weapons and equipment in exercises this week in the South China Sea, where territory is claimed by several regional states.
U.S. warships conducted what they call "freedom of navigation" patrols through the South China Sea over the past year amid growing concern about Chinese construction of air strips and docks on disputed reefs and islands.