A group of 65 Ukrainian military personnel has completed training in the United States on the Patriot air defense system and returned to Europe, the US Department of Defense said Thursday.

65 Ukrainian soldiers underwent training on how to operate the Patriot system at the Fort Sill base in Oklahoma, the United States. They were expected to continue preparations for operating the system in Europe once they finish training in the United States.

In January, Russian Ambassador to the US Anatoly Antonov said the Pentagon's decision to train Ukrainian personnel to operate and maintain Patriot missile defense systems at the US Army post in Fort Sill, Oklahoma, was proof of Washington’s involvement in the war in Ukraine.

US President Joe Biden had said in December that he intended to supply Ukraine with patriot missile systems, underlining that "We are going to continue to strengthen Ukraine's ability to defend itself, particularly air defense. That's why we're gonna be providing Ukraine with a Patriot missile battery and training Ukrainian forces to use it."

"This week, 65 Ukrainian air defenders completed Patriot training at Fort Sill, Oklahoma, and have now arrived back in Europe," Pentagon spokesman Brigadier General Pat Ryder told journalists.

"They're integrating with other Ukrainian air defenders along with donated Patriot air defense equipment from the United States, Germany, and the Netherlands," he said.

The United States has been a training ground for more than 7,000 Ukrainian military personnel since the outbreak of the Ukrainian war in February 2022.

The MIM-104 Patriot, produced by US defense firm Raytheon, is a surface-to-air missile system initially developed to intercept high-flying aircraft.

It was modified in the 1980s to focus on the new threat of tactical ballistic missiles and was used in combat against Iraq's Russian-made Scuds in the 1991 Gulf War.

However, US National Security Council Strategic Communications Coordinator John Kirby said earlier in March that Patriot systems sent to Ukraine won't be a match in efficiency in the face of Russian cruise missiles and drones.   

"The Patriot missile system is really designed to go after ballistic missiles. It is not as effective on cruise missiles, and it certainly cannot be effective against drones," Kirby stated to CNN, adding that possibilities to fend off hypersonic missiles are "limited."  

Kirby described fighting hypersonic missiles as "very, very difficult" but also did not hesitate to add that it would not "surprise" him if "Ukrainian air defenses are limited in their ability to go after hypersonic missiles."