BEIJING (AP) — China responded sharply to Washington's accusations over a confrontation at sea, an incident that analysts said could become more common as Beijing strengthens its navy and asserts claims to adjacent waters.

The US accused Chinese ships of surrounding and harassing its Navy vessel in international waters, coming within 25 feet of the USNS Impeccable, stopping dead in front of it and strewing debris in its path. Some of the Chinese crew even stripped to their underwear after a blast by US fire hoses.

But China's Foreign Ministry said the American vessel "broke international and Chinese laws in the South China Sea without China's permission."

Sunday's incident will likely be discussed when Foreign Minister Yang Jiechi visits Washington this week.

The US Embassy in Beijing lodged a protest with the Foreign Ministry and said the Navy mapping vessel had been conducting "routine operations ... in accordance with customary international law."

US National Intelligence Director Dennis Blair said Chinese policies "seem to be in a more military, aggressive" stance. "That is a trend that we are seeing," he told the Senate Armed Services committee.

It was still unclear, he said, whether China was using its growing military power "for good or pushing people around."

The latest confrontation between US surveillance craft and Chinese coastal defences took place in international waters in the South China Sea about 75 miles south of China's Hainan Island, the home of numerous Chinese naval installations.

Blair called the incident "the most serious" since a Chinese military plane collided with a US electronic surveillance plane also off Hainan in April 2001, the early months of former President George W. Bush's presidency.

A Chinese pilot was killed, and the U.S. plane made an emergency landing on the island. The crew was released 10 days later, and the plane was also later returned.

The director of the US Defense Department Intelligence Agency, Lt. Gen. Michael Maples, told the committee that China was strengthening its ability to conduct military operations along its periphery "on its own terms," and acquiring sophisticated air defences from Russia that would greatly extend its capabilities.

"It is building and fielding sophisticated weapon systems and testing new doctrines that it believes will allow it to prevail in regional conflicts and also counter traditional US military advantages," DIA director Maples said.

Observers said Beijing appeared to be asserting its claim to refuse rights to foreign navies wanting to carry out surveillance within its 200-mile exclusive economic zone.

The zone, under international law, gives a state certain rights over the use of natural resources there. But the US-China confrontation is military in nature.

"China considers that international law only allows innocent passage for military vessels in its zone, not activities that could be considered to have a military purpose," said Shen Dingli, director of the Center of American Studies at Shanghai's Fudan University.

That clashes with one of the cardinal principles of America's doctrine of ocean navigation: the right to unrestricted passage in international waters as long as vessels are not encroaching on the economic interests of the country it is passing.

While the US has offered talks on the issue, neither side appears willing to compromise.

China has recorded at least 200 instances of US vessels collecting intelligence in China's exclusive economic zone, but generally chose to avoid confrontation, said Guan Jianqiang, an international law expert at Shanghai's East China University of Politics and Law.

The latest incident had overtones of spycraft, but the US ship is not, strictly speaking, a spy ship. It maps the ocean floor with sonar, compiling information the Navy can use to steer its own submarines or track those of other nations.

Hainan hosts numerous naval and air force installations and is the home of Beijing's newest submarine base.

An overall naval upgrade is adding advanced missile destroyers, diesel electric submarines, and possibly one or more aircraft carriers in coming years.

The US and others are eager to learn more about those programs and their eventual aims, although Beijing has largely dismissed calls for greater transparency. Keeping out prying eyes and ears is a key priority.

"For the foreseeable future, China will continue to test the waters to see to what extent they can dissuade the US from taking such a close interest," said Ron Huisken of the Australian National University's Strategic and Defense Studies Center.

The naval upgrade comes alongside a growing diplomatic assertiveness in Beijing, particularly in backing up its claims to extensive maritime territories to the east and south.

China views almost the entirety of the South China Sea as its territory. Its claims to small islets in the region have put it at odds with five governments — the Philippines, Vietnam, Malaysia, Brunei and Taiwan.