WASHINGTON -- A Russian and Chinese naval formation patrolled "near Alaska" last week but "was not considered a threat," U.S. Northern Command said Sunday.
"Air and maritime assets under our commands conducted operations to assure the defense of the United States and Canada," a NORTHCOM statement to ABC News said, adding that "the patrol remained in international waters and was not considered a threat."
A U.S. official also told ABC News that the Pentagon had been tracking and expecting this patrol for several weeks, since well before the exercise began. Four U.S. destroyers and P-8 aircraft were also sent to shadow the patrol.
The Wall Street Journal was the first to report on the formation.
Russia has not publicly commented, though a spokesman for the Chinese Embassy in Washington told the Journal in a statement: "According to the annual cooperation plan between the Chinese and Russian militaries, naval vessels of the two countries have recently conducted joint maritime patrols in relevant waters in the western and northern Pacific Ocean."
"This action is not targeted at any third party and has nothing to do with the current international and regional situation," the spokesman said.
The Journal reported that the formation involved 11 Chinese and Russian ships -- and that number was echoed by U.S. lawmakers.
The move represents an apparent show of force by China and Russia. The two countries have increased their ties amid tensions with the U.S. over Taiwan and Ukraine, respectively.
Alaska's senators, Lisa Murkowski and Dan Sullivan, both Republicans, spoke out against the exercise in statements while reiterating their call for more military funding for their state.
"This is a stark reminder of Alaska's proximity to both China and Russia, as well as the essential role our state plays in our national defense and territorial sovereignty," Murkowski said, in part.
"We have entered a new era of authoritarian aggression led by the dictators in Beijing and Moscow," Sullivan said. "In recognition of this reality and our state's unrivaled strategic location, for years, I've been pressing the Navy and each successive administration to commit to a greater Naval, Coast Guard, and Marine Corps presence in Alaska, more Arctic-capable vessels, and more infrastructure."
ABC News' Benjamin Siu contributed to this report.