Ukrainian President Petro Poroshenko says that not all of the information on Kyiv's military-technical cooperation with the United States can be made public.

"I am in awe of [U.S. Defense Secretary James] Mattis. We had a very good visit by [Ukrainian Defense] Minister [Stepan] Poltorak. We had specific timeframe for developing our cooperation, including in the military-technical sphere, including [arms] supplies, including and not only, and not so much of, the kind of weapon being constantly discussed," Poroshenko said at a briefing in Munich on Saturday.

"But unfortunately I cannot disclose this information," he said.

Poroshenko said he was grateful to the U.S. for increasing the scale and scope of cooperation.