The U.S. will begin training Ukrainians on how to use the Patriot missile system as early as next week, CNN reported.

The news network attributed the information to two U.S. officials familiar with the matter.

The site of the training, which is expected to take "several months," is Fort Sill in Oklahoma.

"I'm not going to be able to give you a specific time frame for the completion of the training," said Laura Cooper, the deputy assistant secretary of defense for Russia, Ukraine and Eurasia.

In late December, the U.S. said it would send the complex missile system to Ukraine. The announcement came when Ukrainian President Volodymyr Zelenskyy visited Washington, D.C.

Reuters noted that Zelenskyy told Congress during his visit that U.S. aid to his country was an investment in democracy.

He said the Patriot system was a key step in creating an air shield.

"This is the only way that we can deprive the terrorist state of its main instrument of terror — the possibility to hit our cities, our energy," Zelenskyy told a White House news conference.

The Patriot missile defense system, made by Raytheon, is the most sophisticated surface-to-air missile defense system NATO has at its disposal. It is designed to track and take on inbound ballistic and cruise missiles and aircraft.

Though the Patriot system widely is seen as advanced, Russian President Vladimir Putin has dismissed it as "quite old," telling reporters Moscow would find a way to counter it, according to Reuters.

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