1005 GMT April 21, 2019
"We have forces deployed throughout the region to demonstrate the United States commitment to freedom of navigation," he told reporters in Seoul on Monday, Press TV reported.
He said that the recent mission allowed him to see "first-hand" new operational capabilities in the fleet.
The US Pacific Fleet announced on Sunday that the admiral joined the seven-hour surveillance mission on Saturday.
It added that Adm. Swift witnessed the full range of capabilities of the P-8A Poseidon plane during the spying flight.
The admiral "was pleased with the capabilities of the Poseidon," said US Navy Capt. Charlie Brown, a Pacific Fleet public affairs officer who flew with Swift on board the aircraft.
Admiral Swift said communications with China at sea were "positive and structured," without giving further details about the flight.
However, China condemned the mission and said the measure was "provocative."
Washington is stepping up its pressure on China after Beijing decided to build artificial islands in the South China Sea.
The US has stepped up surveillance flights over the Chinese construction projects during the past months.
The Chinese navy in May issued warnings to a US surveillance plane flying over the islands.