A combined Chinese and Russian naval convoy, including a guided missile cruiser and a destroyer have been spotted close to an Alaskan island by the US Coastguard.
The Honolulu-based vessel monitored the ships before they broke formation and dispersed.
A C-130 Hercules provided air support from the Coast Guard station in Kodiak.
"While the formation has operated in accordance with international rules and norms, we will meet presence with presence to ensure there are no disruptions to US interests in the maritime environment around Alaska," Rear Admiral Nathan Moore, Seventeenth Coast Guard District commander, said.
The Coast Guard said Operation Frontier Sentinel guidelines call for meeting "presence with presence" when strategic competitors operate in and around US waters.
The incident came a month after NATO Secretary General Jens Stoltenberg warned about China's interest in the Arctic and Russia's growing military build up there.
He said Russia had set up a new Arctic Command and has opened hundreds of new and former Soviet-era Arctic military sites, including deep-water ports and airfields.
China has declared itself a "near Arctic" state, he added, and plans to build the world's largest icebreaker.
"Beijing and Moscow have also pledged to intensify practical cooperation in the Arctic. This forms part of a deepening strategic partnership that challenges our values and interests," Mr Stoltenberg said in a visit to Canada's north.
It is not the first time Chinese naval ships have sailed close to Alaskan waters.
In September 2021 Coast Guard cutters in the Bering Sea and North Pacific Ocean encountered Chinese ships around 50 miles (80km) off the Aleutian Islands.