SINGAPORE — Chinese military officers put on a charm offensive at a security forum over the weekend, surprising delegates at a time when Beijing is making decisive claims to territory across Asia’s seas — but observers warned words should be put into action before the Chinese could be taken seriously.

No one expected any resolution of disputes over maritime boundaries, accusations of Chinese cyberespionage, Beijing’s suspicions about the US "pivot" to Asia or other prickly issues at the annual Shangri-La Dialogue in Singapore. But the charm offensive by the senior People’s Liberation Army (PLA) officers, less than a week before Chinese President Xi Jinping meets US President Barack Obama for an informal summit, appeared to be designed to tone down inflammatory issues by emphasising co-operation and talks.

"There’s no question that this year the PLA delegation has come very prepared to engage in dialogue," said John Chipman, director-general of the London-based International Institute for Strategic Studies, which convenes the forum.

"The intensity of the Chinese engagement and the manner of their engagement is different."

The defence minister of the Philippines, Voltaire Gazmin, also noted a shift. "It’s a total turnaround. They have been talking about peaceful resolutions, not outward acts," Mr Gazmin said. "But we still hope to see that these words are put into action."

China claims large swathes of the South China Sea, which could be rich in oil and gas. The Philippines and other Southeast Asia nations have challenged those claims. Beijing is also embroiled in a row with Tokyo over uninhabited islands in the East China Sea, which are also believed to contain large energy deposits.

China, the world’s second-largest economy and a rising military power, is aware it needs what it calls a "stable and peaceful external environment" for its own development. "China’s development and prosperity is a major opportunity instead of a challenge or even threat to countries in the Asia-Pacific region," Lt-Gen Qi Jianguo, the PLA’s deputy chief of the general staff, said.

Lt-Gen Qi, China’s top official at the forum, said dialogue "by no means denotes unconditional compromise" and he gave no ground on sovereignty claims, calling the presence of Chinese warships in the East China Sea and the South China Sea "totally legitimate and uncontroversial to patrol within our own territory".

But he said "China is a peace-loving nation".

Unlike most other countries, China has sent its defence minister to the Shangri-La Dialogue only once — in 2011.

Despite that absence, a senior US official accompanying Defence Secretary Chuck Hagel to the forum saw a big change in the Chinese delegation. "Last year China had a very, very small contingent, a relatively junior-ranking contingent. This year they came in force … and have been very active in the panels," said the official. "That’s very good. We want everybody to engage."

While there was some scepticism about China’s position, the Chinese were not shy about taking tough questions. Maj-Gen Yao Yunzhu of the PLA’s Academy of Military Science asked Mr Hagel how Washington could reassure Beijing that the US focus on Asia was not an "attempt to counter China’s rising influence".