A touch of irony surfaced a week ago when an American destroyer patrolling in the South China Sea sailed to the aid of the U.S. ocean surveillance ship Impeccable, which was being harassed by three Chinese government vessels and two trawlers.

The American warship was the USS Chung-Hoon, named for a Chinese-American naval officer awarded the Navy Cross, the nation's second-highest combat decoration, for heroic action against Japanese kamikaze planes in World War II. The late Gordon P. Chung-Hoon, of Hawai'i, retired as a two-star admiral in 1959, and his namesake ship's home port is Pearl Harbor.

That warship could outrun, outmaneuver, and outgun the Chinese ships on the scene but arrived after the incident to warn the Chinese not to return. The Impeccable resumed its mission of mapping the floor of the treacherous sea filled with islands, atolls, rocks, banks and reefs, and gathering intelligence on Chinese submarines based on the island of Hainan, 75 miles away.

This confrontation, however, was far more than a skirmish at sea. It has turned into an early test for President Obama, who is scheduled to meet with Chinese President Hu Jintao at the G20 economic summit meeting in London in April. Sino-U.S. military relations are certain to be on the agenda.

A question being addressed in the Pacific Command's headquarters above Pearl Harbor was whether the Chinese assault had been ordered by the political authorities in Beijing or had been mounted by the People's Liberation Army that comprises all of China's armed forces.

"It's hard to tell," an American analyst said. "But the PLA sometimes goes off on its own without telling anyone."

The educated consensus held that the confrontation was authorized by Beijing because it was conducted so deliberately and was timed to test the new American president.

In addition, spokesmen for China's leaders were immediately prepared to assert that the U.S. had intruded into China's territorial waters. In contrast, when Foreign Minister Yang Jiechi was in Washington to meet with President Obama, all the White House would say was that the national security adviser, Gen. James Jones, had "raised the recent incident in the South China Sea."

The concern among U.S. military officers in the Pacific was that the Chinese would miscalculate in the future and overtly threaten to attack an American warship. Since the ship's captain would have the inherent duty to defend his ship, he could order his crew to fire on the Chinese. The consequences would be incalculable.

A White House press release said President Obama "stressed the importance of raising the level and frequency of the U.S.-China military-to-military dialogue in order to avoid future incidents." The Chinese broke off those meetings after the Bush administration announced in October that the U.S. would sell $6.5 billion worth of weapons to Taiwan.

The Pacific Command, led by Adm. Timothy Keating, has been trying to revive that dialogue, with staff officers saying the South China Sea incident makes such contacts imperative. The admiral met quietly with senior Chinese officers in Hong Kong last month, but to no avail. A Pentagon official, David Sedney, was in Beijing on a similar mission, but went home empty-handed.

At issue, moreover, is freedom of the seas, which is critically important to the U.S. China claims most of the South China Sea as territorial waters under Beijing's control. The U.S. and most Asian nations disagree; much of their economic lifelines pass through that sea. That passage is also vital to U.S. warships sailing between the Pacific and Indian oceans.

China and the U.S. agreed in 1998 to set up a consultative mechanism so that warships that encountered each other would have procedures to communicate, interpret the rules of the nautical road and avoid accidents. It was signed by Secretary of Defense William Cohen and Minister of National Defense Chi Haotian.

With this incident and others, such as a Chinese fighter plane buzzing a U.S. intelligence aircraft in the same area in 2001 only to collide with it and drop out of the sky, that agreement appears to have been thrown overboard.