China may also have provided Iran with a long-range early-warning radar that spots stealth aircraft meant to evade detection, people familiar with the matter tell NBC News

The F-15 fighter that was shot down over southwestern Iran last month and set off a dangerous rescue mission was probably struck by a Chinese-made shoulder-launched missile, three people with knowledge of the matter told NBC News.

In the early days of the conflict, China also may have provided Iran with a long-range early-warning radar that spots stealth aircraft that are meant to evade detection, according to one of the people and a U.S. official with knowledge of the matter.

U.S. officials are still investigating the circumstances around the shootdown of the American F-15E Strike Eagle in April, the sources said. It was the first time in decades that a U.S. fighter was downed by enemy fire.