WASHINGTON, D.C.: A Chinese warship sailed within yards of an American destroyer -- forcing it to change course -- in an 'unsafe and unprofessional' encounter as the US vessel was in contested waters in the South China Sea, an official said on Monday.

The USS Decatur guided-missile destroyer was conducting what the military calls a 'freedom of navigation operation' Sunday, when it passed within 12 nautical miles of Gaven and Johnson reefs in the remote Spratly Islands.