The U.S. military is considering using aircraft and Navy ships to directly contest Chinese territorial claims to a chain of rapidly expanding artificial islands, U.S. officials said, in a move that would raise the stakes in a regional showdown over who controls disputed waters in the South China Sea.

Defense Secretary Ash Carter has asked his staff to look at options that include flying Navy surveillance aircraft over the islands and sending U.S. naval ships to well within 12 nautical miles of reefs that have been built up and claimed by the Chinese in an area known as the Spratly Islands.