A top US Navy admiral on Monday confirmed that he had been aboard a seven-hour surveillance flight over the South China Sea, a move analysts said indicates that the US is becoming more assertive in regional matters.

US military aircraft have been conducting frequent, wide-ranging close surveillance of China, "which has severely damaged the bilateral mutual trust and jeopardized China's security interests," China's Ministry of Defense (MOD) said in a statement sent to the Global Times on Monday, which also said that it is firmly against such activities.

Admiral Scott Swift, commander of the US Pacific Fleet, confirmed at a press roundtable in Seoul, South Korea, that he had been aboard a P-8 surveillance plane on Saturday, but gave no specific details about the flight.

Swift said his flight was routine, like the earlier flight that carried a CNN team, Reuters reported.

The May CNN report revealed that a US surveillance aircraft received eight warnings from the Chinese navy, asking the plane to leave as it swooped over some of the islets of the Nansha Island chain in the South China Sea.

The MOD also called on the US to keep its promise not to take sides on South China Sea issues and make more contributions to regional peace and stability.

"The surveillance is a signal that the US has grown increasingly keen on pushing forward its strategic rebalance toward the Asia-Pacific, featuring a more in-depth intervention in the South China Sea," Wang Xiaopeng, a maritime border expert at the Chinese Academy of Social Sciences, told the Global Times.

Military intervention

Zhu Feng, a professor of international security at Nanjing University, also warned that more substantial activities may be carried out by the US military in the South China Sea with a rising tendency of military intervention on a wider range.

"We have forces deployed throughout the region to demonstrate the US commitment to freedom of navigation," said Swift, adding the flight allowed him to see "first-hand" new operational capabilities in the fleet.

The intermittent tough stance posed by the US is actually aimed at supporting the Philippines and Japan which will continue to complicate stability in the South China Sea, Wang said, adding that the US has shifted its strategic policy to rely more on its allies in the region due to inadequate financial and strategic investment.

"Creating a hyped-up China threat to the South China Sea will help laws get passed in Japan and the Philippines to strengthen military cooperation with the US, which would help pave the way for the US to complete its containment strategy against China," Wu Shicun, president of the National Institute for the South China Sea, told the Global Times.

Japan's top military commander, Admiral Katsutoshi Kawano, said Thursday that it is possible that Japan would conduct surveillance activities in the South China Sea in future and that there had been "talk" of Japan conducting such patrols, Reuters reported.

Maintaining pressure

Analysts said that the US surveillance flight was also aimed at maintaining pressure on China, even after the completion of land reclamation projects in the area, which has concerned some neighboring countries in the region.

China has completed some of its land reclamation work in the Nansha Islands and is set to start building facilities on the reclaimed land to fulfill its functional requirements, China's foreign ministry said on June 30.

US influence in the region will be compromised as long as China continues its construction on the land, Zhu said, adding that the US expects China to make concessions under its military deterrence

"It is also aware that in a few years, when China has a strong navy, the US' [military] capacity will not match its ambitions," he said.

Meanwhile, China's Maritime Safety Administration announced Monday that the Chinese navy will conduct military drills in the South China Sea to the east of Hainan Province from Wednesday to July 31.

"The drills will demonstrate the determination and capability of China to safeguard its interests at sea as well as regional stability," Wang said, emphasizing that the drills do not target any country.