U.S. military officials confirmed Tuesday that an “irregular air patrol” by three F-22 fighter jets from Honolulu this weekend was connected to a large Russian military exercise off the coast of Hawaii.

The Russian navy is conducting what Russian officials are calling its largest exercise in the Pacific Ocean since the end of the Cold War. The exercise, which is taking place about 400 miles west of Hawaii, includes a variety of warships, anti-submarine aircraft, fighter jets and long-range bombers. 

U.S. military officials confirmed that the F-22’s scrambled Sunday in response to Russian bombers moving close to American air space, although Russian warplanes did not actually enter Hawaii’s air space and the American jets later returned to base.

“U.S. Indo-Pacific Command is monitoring the Russian vessels operating in international waters in the Western Pacific,” Capt. Mike Kafka said in an e-mail. “As part of our normal daily operations, we closely track all vessels in the Indo-Pacific area of operations through maritime patrol aircraft, surface ships and joint capabilities.”

The Russian exercise takes place as President Joe Biden travels to Geneva for a summit with Russian President Vladimir Putin. It’s Biden’s first meeting with Putin since his inauguration in January.

Hawaii is a critical hub for U.S. military operations. U.S. Indo-Pacific Command, which is headquartered out of Camp Smith on Oahu, oversees all operations across the Pacific Ocean, much of the Indian Ocean and parts of the Arctic region. 

Though that has meant most of its attention is on China and North Korea, Russia, which maintains its own Pacific Fleet, is deeply interested in American capabilities in the region, particularly as the U.S. Navy increasingly factors the Arctic into its planning.

Melting polar icecaps have been opening up new trade routes between Europe and the Pacific along with potential undersea energy deposits that Russia and China are eager to secure. 

American fishermen in the Arctic and Northern Pacific have reported increasing interactions with Russian military ships and aircraft that have occasionally been confrontational.

Last month the U.S. Pacific Fleet tracked a Russian spyship, the Vladivostok-based Kareliya, lingering about 15 miles to the west of Kauai. 

Kauai is the site of the Pacific Missile Range Facility Barking Sands, which is used by the Navy and the Missile Defense Agency to test-fire missiles. The Kareliya’s presence prompted American commanders to delay a missile test. A Russian spyship also lingered in Hawaiian waters in 2016 to monitor the biennial U.S.-hosted Rim of The Pacific naval exercise.

However, while the U.S. military says it’s monitoring these activities closely, most are well within the bounds of international law. The U.S. military also frequently moves ships and sometimes trains near Russia and China.

“We operate in accordance with international law of the sea and in the air to ensure that all nations can do the same without fear or contest and in order to secure a free and open Indo-Pacific,” said Kafka. “As Russia operates within the region, it is expected to do so in accordance with international law.”