A crew member on a Chinese trawler uses a grapple hook in an apparent attempt to snag the towed acoustic array of the military Sealift Command ocean surveillance ship USNS Impeccable (T-AGOS-23) in the South China Sea in this picture taken March 8, 2009 and released March 9. REUTERS/U.S. Navy/Handout

WASHINGTON (Reuters) - China’s dispute with the United States over accusations it harassed a U.S. naval vessel is the worst between the two countries since the detention of a U.S. spy plane and crew in 2001, the top U.S. intelligence official said on Tuesday.

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.”

His comments came a day after the United States accused China of harassing a U.S. naval survey ship, the USNS Impeccable, in international waters off a Hainan island, a key strategic base from which China projects military power in the South China Sea.

China rejected the accusation and charged the United States with violating Chinese laws regarding its disputed exclusive economic zones.

Blair called the incident “the most serious” since a Chinese military plane collided with a U.S. 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 Defense 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 defenses 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 U.S. military advantages,” he said.