WASHINGTON — China moved Tuesday to ease its conflict with Southeast Asian neighbors over its territorial claims, releasing Vietnamese fishermen jailed for working in disputed waters and softening its language at a meeting of defense ministers.

The moves suggested Beijing is rethinking its aggressive assertion of claims over disputed waters and islands, which has heightened tensions with its neighbors.

At a meeting in Hanoi, Vietnam, with defense ministers from the Association of Southeast Asian Nations, Chinese officials avoided their previous declarations that the South China Sea is a “”core interest.”” The phrase has been interpreted as a sign that Beijing would not yield on its claims in the resource-rich sea. Six countries assert sovereignty over portions the waters.

China’s defense minister, Liang Guanglie, also said in his remarks at the forum that China was prepared to cooperate on regional security issues and insisted that China’s military expansion was not a threat to its neighbors.

China on Tuesday released the nine fishermen it had jailed Sept. 11 near the Paracel archipelago, in what it said was a goodwill gesture.

China’s disputes with its neighbors have been a flashpoint repeatedly this year.

Last month, Japan jailed a fishing captain after he collided with Japanese vessels, causing China to cut off deliveries of some valuable minerals to Japanese industry for three weeks. In July, U.S. Secretary of State Hillary Rodham Clinton urged Southeast Asian nations to band together to negotiate with China over the issue, drawing a sharp reaction from Beijing.

Analysts say that while senior military officials and some other Chinese leaders want the government to take a forceful stand on the claims, many other top leaders are eager to avoid a collision over the issue.

U.S. officials also sought to soften their approach to the issue. They said they took no position on the claims, and did not intend to try to mediate the issue.

At the same time, U.S. Defense Secretary Robert M. Gates asserted again that the United States has a “”national interest”” in freedom of navigation, and intends to continue military exercises in the region, despite opposition from China.