Hard diplomacy ahead despite China showing its softer side

510390193LZ034_Sultan_Tuank
Lintao Zhang | Getty Images | Getty Images

From a military rules-of-the-road agreement with Washington to $20 billion in loans for Southeast Asia, Beijing has set aside the tensions of recent years to present a softer side to the world in the last week.

But proof of whether President Xi Jinping is serious about narrowing differences that have marked his first two years in office will depend on how China's festering disputes are managed in the months ahead.

The possibilities for disagreement are many, from cyberspying to land reclamation in the disputed South China Sea and the deeply emotional issue for China of how Japan deals with next year's 70th anniversary of the end of World War Two.

Read MoreChinese hack US weather systems, satellite network: Wash Post

China set nerves on edge with its air defense zone over the East China Sea, by sending an oil rig deep into waters disputed with Vietnam and by unveiling advanced new weapons, including a prototype stealth fighter.

But in recent days, China has gone out of its way to set minds at ease as Xi hosted the Asia Pacific Economic Cooperation (APEC) summit.

China made conciliatory gestures to Vietnam, the Philippines and Japan, and, with U.S. President Barack Obama, agreed to a climate deal and to lower the risk of misunderstandings during military encounters.

"We still have to observe what happens in the next six to 12 months or even longer. But I think that now we stand at the beginning of a substantive change in Chinese foreign policy," said Shi Yinhong, head of the Centre for American Studies at Beijing's Renmin University who has also advised the government on diplomatic issues.

Reliance on the military has been replaced by money to guide China's diplomacy, Shi added, pointing to the $40 billion New Silk Road fund and $50 billion China-backed Asian Infrastructure Investment Bank announced before APEC.

More than $120 billion has been promised since May to Africa, Southeast Asia and Central Asia.

Read MoreChinese naval push could affect global trade

"The message is that China sincerely hopes that it can play its role as a responsible power," the official China Daily newspaper wrote in an editorial on Monday.

Root causes remain

The root causes of past disagreements have, for now, been set aside.

State-run Xinhua news agency sought to temper expectations following Xi's meeting with Obama last week, saying that, despite the "amicable tone", "still much has to be done to translate promises into reality".

As if to remind the United States of China's growing military power, the day before Xi and Obama's summit, the Chinese military unveiled a sophisticated new stealth fighter jet at an air show in the south of the country.

"A lot of problems exist and there will be a lot of uncertainty in the days to come," said Jia Qingguo, dean of the School of International Studies at Peking University who has also advised the government on diplomacy.

China has long sought to address fears in the region, and globally, that economic growth will inevitably bring a more muscular diplomatic and military approach.

During a summit of Southeast Asia leaders in Myanmar last week, Chinese Premier Li Keqiang proposed a friendship treaty, yet held to the line that Beijing will only settle South China Sea disputes directly with other claimants.

Philippine President Benigno Aquino said he and Xi had a good meeting in Beijing, but the Philippine military says there has been no sign of China reducing its presence in parts of the South China Sea that Manila also claims.

Legacy of ware lives on

Then there is Japan.

China and Japan, the world's second- and third-largest economies, have argued bitterly for two years over disputed islands, regional influence and the legacy of Japan's wartime occupation of China.

While Xi and Japanese Prime Minister Shinzo Abe held breakthrough talks just before APEC, in recognition of the economic damage inflicted by their row, suspicion runs deep.

"Whether or not incidents or disturbances can be prevented from happening again between the two countries depends on Japan's attitude and actions," Han Zhiqiang, acting Chinese ambassador to Japan, was quoted saying in state media last week.

Read More Abe & Xi: From handshake to highfive?

China has already promised high-profile events to mark next year's World War Two anniversary, offering another opportunity to accuse Japan of not properly atoning for its past.

"Japan is particularly worried about how the anniversary will be handled in China," said one Beijing-based Western envoy.

India presents another problem, with no sign of lasting resolution to a festering border dispute.

In recognition of the world's concerns, Xi, speaking to Australia's parliament on Monday, channelled an ancient expression to assuage worries: "A war-mongering state will eventually die no matter how big it is".

He did not finish the saying, whose last line reads: "Though the world is peaceful, you will be in danger if you forget about preparing for war".