G20 leaders met on Monday under pressure to reboot the world economy, but a stumbling push for a Syria ceasefire and Asia's heated territorial disputes intruded on the summit in Hangzhou.

There had been hopes of a breakthrough in stemming the Syria conflict after the US said it was close to a deal with Russia. But frantic diplomacy ended in failure, with Moscow accused of backtracking.

A US official said "differences remain" despite two rounds of talks between Secretary of State John Kerry and his counterpart Sergei Lavrov on the sidelines of the summit.

Presidents Barack Obama and Vladimir Putin also met Monday, but it was far from clear that they could find agreement on the intractable five-year crisis, in which the two support different sides.

The Group of 20 developed and emerging economies -- this year gathering in a scenic eastern Chinese city which is largely deserted under a sweeping security operation -- represents 85 percent of the world's GDP and two-thirds of its population. 

China's President Xi Jinping has urged the leaders to avoid "empty talk" and confront rising protectionism that threatens globalisation and free trade.

But experts fear the gathering will be short on substance, with no acute crisis pushing leaders to defy rising populist sentiment and to take difficult steps such as liberalising trade.

- Trouble spots -

There were also plenty of distractions serving as reminders of the geopolitical forces swirling around China, which sees the summit as a showcase for its global leadership credentials.

North Korea reportedly fired three ballistic missiles off its east coast Monday in its latest show of force, some two weeks after it test-fired a submarine-launched ballistic missile.

China is North Korea's main patron and protector but has been either unwilling or unable to rein in its nuclear and missile ambitions that have sent tensions soaring across East Asia and beyond.

Xi told South Korea's President Park Geun-Hye that Beijing opposed the US deployment of the THAAD anti-missile system in her country.

The Chinese leader will Monday also meet Japan's nationalist Prime Minister Shinzo Abe, their first encounter in more than a year with their nations divided by territorial disputes and recriminations over history.

"There are difficult issues between Japan and China, and because of that, it is important that the leaders exchange honest opinions and make improvements," said Tokyo's chief cabinet secretary Yoshihide Suga.

Beijing and Tokyo have a longstanding dispute over islands in the East China Sea controlled by Japan, which knows them as Senkaku, and claimed by China which calls them Diaoyu.

The last time the two met on Chinese soil, on the sidelines of an APEC summit in 2014, they could barely conceal their mutual distaste.

Ties later thawed, but tensions have risen again as Japan weighs in on another dispute in the South China Sea, where Beijing has built artificial islands capable of supporting military facilities.

A new flashpoint is emerging his week, with the Philippines asking Beijing to explain the presence of Chinese vessels near the disputed Scarborough Shoal.

Chinese dredging in the area -- just over 200 kilometres from the Philippines’ main island of Luzon, where US forces have a regular presence under a military pact -- would represent a major escalation.

- Populism swirls -

China is intent on keeping the G20 on script. In an opening speech Sunday Xi delivered a stern warning over sluggish global growth, financial market turbulence and receding global trade and investment.

"We hope the Hangzhou summit will come up with a prescription for the world economy and lead it back to the road of strong, balanced, comprehensive and sustainable growth," he said.

But the talks take place amid a perception that the global economic order exemplified by the G20 is not working for ordinary people.

"Globalisation is not only positive, it can also engender inequalities between different groups, different populations," Germany's Angela Merkel told reporters on her arrival in Hangzhou.

She warned against the temptation for countries to look inwards, with "protectionist measures that put the brakes on growth", but added: "The fight against inequalities is an important theme to firmly connect growth and social justice."

French President Francois Hollande said: "France is for globalisation, but on condition that it is regulated, that there are principles, standards, particularly for the environment, for society."

Britain's vote to leave the European Union -- so far the most striking manifestation of the global mood -- leaves it with the task of renegotiating access to the markets of the rest of the world.

New Prime Minister Theresa May sought to get a head-start in Hangzhou, meeting Australia's Malcolm Turnbull who said they have "already been engaged in discussions" on a framework for a trade deal.

But EU commission chief Jean-Claude Juncker said he opposes such talks while Britain remains part of the European Union.

Trade negotiations were an "exclusive matter" for the European Union on behalf of its members and "we are sticking to it", he told reporters Sunday.

Source: AFP