The United States would like Turkey to remain a NATO member but without Russian-made S-400 air defense systems on its territory, the US envoy to NATO has told foreign journalists.

During a briefing ahead of the April 3-4 meeting of NATO foreign ministers in Washington, US Permanent Representative to the North Atlantic Treaty Organization, Ambassador Kay Bailey Hutchison, evaded a direct answer to a question whether Turkey will be excluded from NATO if it buys Russian-made missile systems.

"Turkey is a very important ally. They are an ally. They are also carrying a heavy load in our NATO missions. They too are a framework nation in Afghanistan, and they are participating in all of our missions and they have since the beginning of NATO. So we want Turkey to stay in the alliance. We want them not to have a Russian missile defense system in the middle of their country that cannot be interoperable with NATO," she said.

"The United States is very concerned about Turkey having our F-35s in proximity to an S-400 Russian system because there could be a transfer of information, communications, or even an interruption of that," the US diplomat added.