Russian President Vladimir Putin says Moscow is helping China build a system warning about ballistic missile launches.
Since Cold War times, only the United States and Russia have had such systems, which involve an array of ground-based radars and space satellites.
The system is essential for early spotting of intercontinental ballistic missiles.
Speaking at an international affairs conference Thursday, Putin said that Russia has been helping China develop such a system.
He added that "this is a very serious thing that will radically enhance China's defense capability."
His statement signaled a new level of defense cooperation between the two former Communist rivals, which have developed increasingly close political and military ties.
