The U.S. Navy deliberately avoided military drills or other actions that could have further inflamed tensions with Beijing during a patrol last week near islands China has built in the South China Sea, U.S. officials said.

"We wanted to assert our rights under international law, but not to the point where we were poking the Chinese in the eye, or where it would unnecessarily escalate the situation," said a U.S. official, speaking on condition of anonymity.

The official said the destroyer USS Lassen turned off its fire control radars while transiting within 12 nautical miles (22 km) of Subi Reef and avoided any military operations during that time, including helicopter launches or other drills.