There was even a joint announcement by China and United States that they would ratify the Paris climate change agreement, a significant step for the world's two biggest emitters of greenhouse gases. But scratch beneath the surface, and the gathering of the world's most powerful leaders was not all plain sailing - from the distraction of a North Korean missile test to the failure of the United States and Russia to reach agreement over Syria, and diplomatic faux pas to double speak over protectionism.

Chinese state media, while largely basking in the glory of a summit that happened without being too overshadowed by disputes such as the South China Sea, also let slip Beijing's frustrations at what it sees as Western efforts to stymie its economic ambitions.

"For the world's major developed economies, they should curb rising protectionism and dismantle anti-trade measures as economic isolationism is not a solution to sluggish growth," China's official Xinhua news agency said late on Monday.

"In order to build an inclusive, rule-based and open world economy, protectionism must be prevented from eroding the foundation for a faster and healthier economic recovery." In the run-up to G20, China has been particularly upset by what it sees as unwarranted suspicion of its overseas investment agenda smacking of protectionism and paranoia.

A few weeks before the summit, Australia blocked the A$10 billion ($7.63 billion) sale of the country's biggest energy grid to Chinese bidders, while Britain delayed a $24 billion Chinese-invested nuclear project.

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