China is quietly testing electronic warfare assets recently installed at fortified outposts in the South China Sea, according to sources who have seen U.S. intelligence reports.

Intelligence assessments, which were curated less than a month ago, say this is the first known use of the equipment since its deployment earlier this year to outposts in the Spratly Islands, said the sources, who spoke on the condition of anonymity.

A Pentagon spokesperson declined to comment on intelligence matters.

The move allows Beijing to further project its power in the hotly disputed waters. The placement of electronic warfare assets, which are designed to confuse or disable communications and radar systems, comes on the heels of China's installation of anti-ship cruise missiles and surface-to-air missile systems on three outposts in the hotly contested waters of the South China Sea.

The new coastal defense systems, coupled with electronic warfare equipment, represent significant additions to Beijing's military portfolio in one of the most contested regions in the world.

The South China Sea, which is home to more than 200 specks of land, serves as a gateway to global sea routes where approximately $3.4 trillion of trade passes annually.

The numerous overlapping sovereign claims to islands, reefs and rocks — many of which disappear under high tide — have turned the waters into an armed camp. Beijing holds the lion's share of these features with approximately 27 outposts peppered throughout.