Speaking earlier in the day, Pentagon spokesman Major Jamie Davis said U.S. forces will fly and sail "wherever worldwide law" allows. "We fly, sail, and operate wherever global law allows", Captain Jeff Davis said.
"Vietnam's future prosperity depends upon a stable and peaceful maritime environment", US Ambassador Ted Osius said.
The Pentagon gave no details of the latest mission.
US Ambassador Ted Osius, fourth from left, inspects patrol boats with Vietnam Coast Guard members during a delivery ceremony, Tuesday, May 23, 2017, in Quang Nam, central Vietnam.
Since Mischief Reef is a "low tide elevation" (according to the UNCLOS arbitral tribunal award from last summer), China can not claim a 12 nautical mile territorial sea around the artificial island it has built there.
But Storey said claims of victory on China's behalf were premature.
The US has challenged annexations of these islets and advocated for a diplomatic settlement of the disputes. MOD spokesman Senior Colonel Wu Qian said such spying activities of US military aircraft and vessels were the "fundamental causes" of problems in security issues between the two countries.
China denies these claims, countering that the U.S. is eager to stoke tensions in the region.
He said that deploying weapons in Hainan was China's own business within the scope of its sovereignty.
"Internationally, the U.S. military can reassure its global allies that it has not lost footing in the South China Sea, and appear tough before the upcoming Shangri-La Dialogue, where defense officials from around the world will meet in Singapore".
The U.S.'s move was aimed at signaling to China that it intends to keep critical sea lanes open, according to the Journal. With more on this and other news around the world we turn to Ro Aram. Why are they doing this?
The meeting with Trump next Wednesday is a coup for Prime Minister Nguyen Xuan Phuc, who will be the first Southeast Asian leader to visit the White House under the new administration.
Even so, this was the first freedom-of-navigation operation since October and since Trump took office in January. "By saying the government will not make further operations public before the annual report, they may seek to avoid the persistent public calls for public FON operations".
Of course, there is one more unintended outcome of leaking the details of FONOPs: China now must publicly react lest it be seen as not sufficiently attentive to its own sovereignty.
"We operate in the Asia-Pacific region on a daily basis, including in the South China Sea".
"We urge the American side to take concrete efforts to correct its wrongdoings and add more positive energy to the military-to-military relationship", Ren said. "And I think that has lent some urgency to their measures".