WASHINGTON, Feb 24 - The United States, which is worried by China's military buildup to assert dominance in the East Vietnam Sea, will increase freedom-of-navigation operations there, a senior Pentagon official said on Wednesday.

"We will be doing them more, and we'll be doing them with greater complexity in the future and ... we'll fly, sail and operate wherever international law allows," Admiral Harry Harris, head of the U.S. Navy's Pacific Command, told a hearing of the House of Representatives Armed Services Committee.

Harris said the U.S. must continue to operate in the East Vietnam Sea to “demonstrate that that water space and the air above it is international.”

On Tuesday, Harris said China was "changing the operational landscape" in the East Vietnam Sea by deploying missiles and radar as part of an effort to militarily dominate East Asia.

“China is clearly militarizing the [East Vietnam Sea] ... You'd have to believe in a flat Earth to think otherwise," Harris said in comments that coincided with a visit to Washington by Chinese Foreign Minister Wang Yi.

China says its military facilities in the East Vietnam Sea are "legal and appropriate," and on Tuesday, in an apparent reference to U.S. patrols, Wang said Beijing hoped not to see more close-up reconnaissance, or the dispatch of missile destroyers or strategic bombers.

Wang met with U.S. national security adviser Susan Rice on Wednesday and they "candidly discussed" maritime issues, the White House said in a statement. Rice emphasized strong U.S. support for freedom of navigation and urged China to address regional concerns, the statement said.

Harris, asked what more could be done to deter militarization, said the United States could deploy more naval assets, although there were significant "fiscal, diplomatic and political hurdles" in the way of stationing a second aircraft carrier group in the region.

"We could consider putting another (attack) submarine out there, we could put additional destroyers forward ...there are a lot of things we could do, short of putting a full carrier strike group in the Western Pacific," he said.

China claims most of the East Vietnam Sea, through which more than $5 trillion in global trade passes every year. Vietnam, Malaysia, Brunei, the Philippines and Taiwan have rival claims.

Harris's comments came a day after he said China had deployed surface-to-air missiles on Phu Lam (Woody) Island in Vietnam's Hoang Sa (Paracel) chain and radars on Chau Vien (Cuarteron) Reef in the Southeast Asian country's Truong Sa (Spratly) archipelago further to the south.

On Tuesday, his command said China's repeated deployment of advanced fighter aircraft to Phu Lam was part of a disturbing trend that was inconsistent with Beijing's commitment to avoid actions that could escalate disputes.

Last month, a U.S. Navy destroyer carried out a patrol within 12 nautical miles of Tri Ton (Triton) Island in Hoang Sa, a move China called provocative.

The United States has also conducted sea and air patrols near artificial islands China has built in Truong Sa, including by two B-52 strategic bombers in November.