* Japan-China islands dispute forces its way onto agenda
* Decisions on radar, port visits to help boost partnership
* Slow, steady approach on military ties with China
ABOARD A U.S. MILITARY AIRCRAFT, Sept 22 (Reuters) - Defense Secretary Leon Panetta's week-long visit to the Asia-Pacific region helped deepen the U.S. military's strategic shift to the area, even as it illustrated the balancing role that Washington may have to play to maintain peace and stability.
The trip, which concluded on Saturday, took Panetta to Japan, China and New Zealand and coincided with a flare-up in tensions between Tokyo and Beijing over a disputed island group in the East China Sea. Anti-Japanese protests took place in dozens of cities across China while Panetta was in the region.
During his visit, Panetta announced a decision to put an additional missile defense radar in Japan to counter the threat from North Korea. He also said Washington had lifted a 26-year-old ban on visits to U.S. military ports by New Zealand's navy.
Both steps further the Pentagon's goal of expanding the military capabilities of partners in the region as part of a shift in strategic focus to the Asia-Pacific announced earlier this year.
Panetta also helped secure a decision to permit flights of the Marine Corps' tilt-rotor V-22 Osprey in Japan, a restriction that had been an irritant to U.S.-Japanese relations and a hindrance to U.S. efforts to restructure its presence in Japan.
But in the days leading up to his visit, the dispute between Beijing and Tokyo over an island grouping in the East China Sea forced its way high onto the agenda.
The dispute worries Washington because Japan is a treaty ally and the United States could be pulled into the conflict should it disintegrate into violence, a point Panetta noted in his meetings with leaders in both countries.
He reaffirmed the U.S. commitment to its treaty obligations, but urged Japan and China to settle their differences diplomatically and peacefully, saying responsible leadership on both sides should avoid further inflaming the issue.
"It is in no country's interest for this situation to escalate into conflict that would undermine peace and stability in this very important region," Panetta told a news conference with Chinese Defense Minister General Liang Guanglie.
He pressed China to agree to a rules-based system, like one proposed by the Association of South East Asian Nations, to resolve territorial disputes in the China Sea between Japan, the Philippines, Vietnam and other countries.
It is not clear whether China is open to U.S. suggestions on the issue. Analysts say Beijing is skeptical of U.S. intentions and suspicious of its expanding military ties in the region.
"They see the U.S. as emboldening nations like Japan, the Philippines and Vietnam, who have territorial disputes with China, to directly confront Beijing," said Bonnie Glaser, a China analyst at the Center for Strategic and International Studies think-tank in Washington.
But with Japan and China locked into their respective positions and no clear way out, Panetta said his discussions led him to believe Beijing was trying to find a mechanism to help resolve the conflicts.
"I think the Chinese are themselves looking for what would be a good format in which to try to resolve these issues for the future," he told reporters. "I felt that they, too, have a concern that these issues can't just be resolved on the fly, that there's got to be a process to try to deal with them."
The main purpose of the defense secretary's trip was to further a military-to-military dialogue with China that began nearly two years ago after a bitter break prompted by U.S. arms sales to Taiwan.
With China modernizing its military and adding weapons that seem to be aimed at countering U.S. strengths, the Pentagon would like to develop more solid relations that can improve communications and avoid miscalculations as the two forces increasingly bump up against each other in the Pacific.
The visit was broadened at the last moment to include a meeting with Vice President Xi Jinping, who will become China's leader next year, and a visit to the naval base at Qingdao, the home port of China's North Sea Fleet.
Glaser said the addition of the fleet visit showed China's military was trying to "demonstrate a degree of transparency." The Xi visit, she said, signaled "the importance that China's current and incoming leadership attaches to Sino-U.S. relations."
Glaser said the bar for judging the success of the visit was not set terribly high.
U.S. officials had hoped to advance the military-to-military dialogue while avoiding the sort of incident that marred former Defense Secretary Robert Gates' visit 18 months ago, when China conducted a test flight of a stealth fighter during his trip.
By those measures, the trip achieved its aims. Chinese officials seemed to relish the dialogue. Most meetings ran longer than scheduled as the two sides explored topics ranging from North Korea to cyberspace.
Chinese military leaders had expressed interest in participating in the multinational Rim of the Pacific naval exercises hosted biennially by the United States. Panetta formally invited them to send a ship in 2014, and U.S. officials said Chinese naval officers seemed pleased.
Although there were no major announcements in China, Panetta said that wasn't expected.
"I have long believed that the United States-China relationship requires a long-term perspective," he told a news conference. "It is measured less by major breakthroughs than by slow steady progress over time to build a relationship and to work on activities in areas of mutual interest." (Reporting By David Alexander; editing by Todd Eastham)