China will be able to project "substantial offensive military power" from artificial islands it has built in the South China Sea's disputed Spratly Islands within months, the director of U.S. national intelligence said.

In a Feb. 23 letter to John McCain, chair of the U.S. Senate Armed Services Committee, James Clapper said Chinese land reclamation and construction work in the Spratlys had established infrastructure needed "to project military capabilities in the South China Sea beyond that which is required for point defense of its outposts."