In the latest in a series of moves that is likely to stoke already heated tensions in the South China Sea, Beijing has sent fighter jets to an island where it has deployed surface-to-air missile batteries, U.S. media said Tuesday.

Citing U.S. officials, Fox News reported that Chinese Shenyang J-11s and Xian JH-7s fighter jets had been spotted over the past few days by U.S. intelligence on Woody Island in the Paracel chain. The isle is where Beijing has deployed HQ-9 missiles, which have a range of about 200 km.

News of the fighter jet deployment came as Chinese Foreign Minister Wang Yi met with U.S. Secretary of State John Kerry in Washington to discuss the South China Sea issue as well as North Korea’s recent nuclear and rocket tests.

Wang sought to tamp down claims of militarization in the waters, saying that “the general situation in the South China Sea is stable compared with other parts of the world.”

He said ship owners and insurers have reported no problems and no commercial vessels have had their passage impeded.

The U.S. Navy conducted what Washington calls freedom of navigation operations near disputed islands in the South China Sea in October and late last month.

Wang also said Beijing would be willing to work with the Association of South East Asian Nations toward a binding code of conduct for the area, something that has eluded the group for years.

“We hope the parties will work together in the same direction — that is to say, nonmilitarization is not the responsibility of one party alone; it’s something that we share,” Wang told reporters after meeting with Kerry.

Wang had been scheduled to visit the Pentagon on Tuesday, but the visit was canceled, a Department of Defense press secretary said, as a “scheduling conflict” had prevented the meeting. It was not immediately clear which side canceled the visit.

China has sent fighter jets to Woody Island before, said Nick Bisley, executive director of the La Trobe Asia program at La Trobe University in Melbourne, Australia. In November, Chinese state media published images showing J-11 fighter jets on the island.

The latest deployment is likely “a statement of intent by China and will be presented as a response to U.S. provocations,” Bisley said.

Tuesday’s dispatch of fighters, however, was the first since Beijing sent commercial airliners in to test the newly built runway on Fiery Cross Reef, one of its artificial islands in the South China Sea in January.

“There’s no breach of military precedent here from the Chinese, as the (People’s Liberation Army) has sent J-11s on temporary detachment to Woody before,” Euan Graham, director of the International Security Program at the Lowy Institute in Sydney, told The Japan Times on Wednesday.

“But clearly an uncompromising message is being sent to coincide with Wang Yi’s visit to Washington, that China is not constrained or deterred from placing surface-to-air missiles, jets or other defense assets on Woody Island,” Graham added.

Any new deployment to Woody Island could spell trouble for U.S. surveillance aircraft, such as the P-8 Poseidon, which fly through the area regularly. In 2014, a Chinese fighter jet came dangerously close to a U.S. Navy P-8 Poseidon patrol aircraft in the vicinity of Woody Island, according to the Pentagon. The fighter flew close to the surveillance aircraft three times, spokesman John Kirby said, flying above, underneath and alongside it. At one point it performed “a barrel roll” in an apparent display of its weapons.

In the short-term, like the missiles deployment last week, the appearance of jets “raises the ante for any overflight the U.S. is planning to do around the Paracels,” Graham said.

But experts say weather concerns as well as the salty sea air makes deployment on off-shore islands difficult for advanced fighters. They say such aircraft are likely only to be deployed for short time frames.

“Stepping back, from a longer-term strategic perspective, this is merely another step toward thickening the PLA’s presence in South China Sea, pushing out south from Hainan,” Graham said, referring to the Chinese island that is home to a naval base with nuclear submarines.

Beyond putting Washington on notice, the move is also likely to affect Vietnam, another claimant to not only the Paracel chain but other areas of the South China Sea as well.

“The military impact will be felt acutely by Vietnam, since the Paracels extends China’s air defense much closer to its eastern seaboard off Da Nang,” said Graham.

Vietnam hosted two Japanese Maritime Self-Defense Force P-3 patrol planes for exercises in the coastal city of Da Nang last week as the aircraft returned from anti-piracy missions in Somalia.

“We should not overlook that as a possible factor, particularly in the context of (Japanese Foreign Minister Fumio) Kishida’s visit to Beijing being abruptly cancelled,” Graham added.

Kishida abandoned plans to visit the Chinese capital this spring after Beijing bridled at criticism by Tokyo of its actions in the South China Sea and its response to North Korea’s rocket launch this month.

Also Tuesday, the head of the U.S. Pacific Command, Adm. Harry Harris, told the U.S. Senate Armed Services Committee that China is “changing the operational landscape” in the South China Sea by sending missiles and constructing radar sites there as part of a gradual effort to militarily dominate the region.

China “is “clearly militarizing” the South China Sea, Harris said. “You’d have to believe in a flat Earth to think otherwise.”

Speaking before the meeting between Wang and Kerry, Harris slammed Beijing for escalating the situation in the disputed waters with the new deployments.

“I believe China seeks hegemony in East Asia,” Harris said when asked about China’s aims in the region.

He restated Washington’s position that regular U.S. air and naval freedom of navigation operations must continue in the area, through which more than $5 trillion in global trade passes each year.

In Tokyo, Chief Cabinet Secretary Yoshihide Suga, the government’s top spokesman, said Wednesday that Japan was gathering and analyzing information on Beijing’s moves in the South China Sea with “serious interest.”

A U.S. think tank reported Monday that Beijing appeared to be installing a high-frequency radar system on Cuarteron Reef in the Spratly Islands that could significantly boost its ability to control the area.

The Spratlys are about 500 km south of the Paracel archipelago.

According to Graham, Beijing appears to be consolidating its gains before the U.S. elects a successor to President Barack Obama.

“Overall, the PLA appears to enjoy a fairly free hand in the South China Sea and are probably quite happy to be given excuses to roll out air defenses” in the South China Sea, Graham said. “This year presents a fairly forgiving external environment in which to lock up gains as far as possible before a new U.S. administration can assert itself.”

He added: “China getting its retaliation in first seems to be a staple of high-level summitry under President Xi (Jinping).”

Information from Reuters added