A group of six Navy vessels was ordered to remain in the Mediterranean Sea instead of moving toward the Middle East to address continuing concerns about the buildup of thousands of troops at the border of Russia and Ukraine.

The decision to stall the USS Harry S. Truman and the five U.S. craft it is traveling with was made by Defense Secretary Lloyd Austin, a defense official told The Associated Press on Tuesday.

The official said the decision was made because naval officials felt a "persistent presence" was needed in Europe to address fears of many in the intelligence and international community about Russia's plans to invade Ukraine next year.

Russia is scheduled to begin separate negotiations with the United States and NATO officials early next year to discuss the country's demands that NATO rejects the admission of Ukraine into NATO, and that the U.S. and its allies reduce the size of their military presence in Ukraine.

Earlier this month, President Joe Biden and Russian President Vladimir Putin spoke on a video call to discuss the issues being raised by both sides, and Biden reportedly warned Putin that his country would face strong sanctions if they acted in a hostile manner toward Ukraine.

USS Harry S Truman, Lloyd Austin, Navy
The aircraft carrier USS Harry S. Truman passes Fort Monroe as it transits the Chesapeake Bay on its way into dock in Norfolk, Va., July 13, 2016. Defense Secretary Lloyd Austin has ordered a U.S. Navy aircraft carrier strike group including the Truman to stay in the Mediterranean Sea region rather than move on to the Middle East, amid worries about the buildup of thousands of Russian troops near the Ukraine border.Randall Greenwell/The Virginian-Pilot via AP File

Keeping the ships in the Mediterranean is necessary in order to reassure U.S. allies and partners in the region, said the official, who spoke on condition of anonymity to discuss military deployment details.

The U.S. and Western allies have watched as the buildup of Russian troops near the border grew to a peak of an estimated 100,000, fueling fears that Moscow was preparing to invade Ukraine.

Russia annexed Ukraine's Crimean Peninsula in 2014 and shortly after threw its support behind a separatist rebellion in the country's east. Over more than seven years, the fighting has killed over 14,000 people and devastated Ukraine's industrial heartland, known as the Donbas.

Russia has denied any intention of launching a new invasion and instead has accused Ukraine of hatching plans to try to use force to reclaim control of the territories held by Moscow-backed rebels. Ukraine has rejected that claim.

The Truman strike group includes five U.S. ships —- the cruiser USS San Jacinto and the guided missile destroyers USS Cole, USS Bainbridge, USS Gravely and USS Jason Dunham. Also with them is the Royal Norwegian Navy frigate HNoMS Fridtjof Nansen.

The Truman left its homeport of Norfolk, Virginia, on Dec. 1, and entered the Mediterranean Sea on Dec. 14. It had been scheduled to continue on into the Gulf region.

The Associated Press contributed to this report.

USS Harry S Truman, Lloyd Austin, Navy
U.S. Secretary of Defense Lloyd Austin speaks during a news briefing at the Pentagon July 21, 2021 in Arlington, Virginia. Austin reportedly ordered the USS Harry S. Truman and the five other U.S. ships it's traveling with to remain in the Mediterranean Sea region instead of continuing its travel plan to address concerns over the number of Russian troops amassing at the country's border with Ukraine.Alex Wong/Getty Images