The new radar systems will enable the Ukrainian military to detect the incoming artillery fire and determine the point where it came from, Poroshenko said, without specifying where the counter-battery systems will be used.

U.S. forces plan to begin training on how to use them as soon as they arrive. U.S. Army officials said the systems will protect against both rocket and artillery attacks.

Russia-backed rebels unload mortars from trucks during a pullback of weapons near Luhansk in eastern Ukraine on Oct. 15. U.S. officials said advanced radar systems being shipped to Ukraine to counter artillery strikes by pro-Russia separatists have been modified to prevent them from peering into Russia.

US Army officials identified surplus radar that could be sent to Ukraine last summer. But the transfer had to be approved by the White House. Officials said giving Ukraine the systems was consistent with the current policy of providing nonlethal defensive material.

The AN/TPQ-36 radar systems have a range of at least 15 miles, and represent a significant advance from the U.S.-provided Lightweight Counter Mortar Radar systems that Ukrainian forces have been using to pinpoint artillery fire. U.S. officials said Ukrainians have developed innovative tactics for the use of the lightweight systems, and hope they will do the same with the larger, longer range systems.