The United States’ Department of Defense (DoD) announced Friday that the U.S. military delivered three lightweight, counter-mortar radar systems to the Ukrainian armed forces on Thursday.

According to a statement released by DoD, the radar systems are the first of 20 that will be delivered to Ukraine over the next several weeks. The DoD also said that U.S. military members would begin training the Ukrainian armed forces in mid-December.

“The radar systems see incoming mortar fire and quickly calculate the point of origin of a mortar round fired by the enemy, and allows friendly forces to react appropriately,” Pentagon spokesman Army Col. Steve Warren said in the statement.

The DoD also stated that it is up to the Ukraine’s armed forces how, where and when they want to use the systems.

“It’s also up to the Ukrainians if they attach these radar [systems] to a fire-direction system, which will allow for counter battery fires, or if they use them independently and react with ground forces,” Warren said.

The radar systems are part of the $118 million in non-lethal equipment and training the U.S. has committed to assisting Ukrainian military.

On Friday, U.S. State Department spokesperson Jeff Rathke announced that lethal military assistance to Ukraine still “remains an option,” while U.S. Senator John McCain told Sputnik that the newly-elected U.S. Congress will pass resolutions to pressurize the U.S. President Barack Obama to offer lethal military assistance to Kiev.

On Thursday, Russia warned the U.S. not to provide arms to the Ukrainian forces. Russian Foreign Ministry spokesman Alexander Lukashevich said that if the U.S. decides to offer lethal weapons to Ukraine, it would be a direct violation of the Geneva Agreements.

During a visit to the U.S. in September, Ukrainian President Petro Poroshenko requested the Obama administration to provide Ukraine with lethal military assistance. However, the U.S. government has so far refused to grant the request.