In an exclusive interview with Fairfax Media ahead of his departure, the Prime Minister said Australia would join Dr Merkel, British Prime Minister Theresa May and other world leaders in pushing the United States on the need for American tech companies to co-operate with national governments and allow encrypted messages sent on messaging platforms such as WhatsApp by suspected terrorists to be accessed. That push is likely to meet fierce resistance from US tech companies. Police monitor protesters who have arrived in Hamburg to rally against the G20. Credit:Andrew Meares Mr Turnbull has also promised to champion free trade, and is expected to hold bilateral meetings and more informal "pull asides" with world leaders including President Trump, Japanese Prime Minister Shinzo Abe and Chinese President Xi Jinping over these matters and the escalating tensions on the Korean peninsula. Ahead of the summit's opening, Mr Trump - who will attend his first G20 summit - let fly a series of tweets that made the questionable claim that trade between China and North Korea had risen by 40 per cent despite calls from Western leaders for China to put more pressure on the hermit kingdom over its latest round of missile tests. "Why should we continue these deals with countries that do not help us?" Mr Trump, who is due to meet Chinese President Xi Jinping and Russian president Vladimir Putin, tweeted.

At an emergency meeting of the UN in New York, the US indicated it could use military force to bring North Korea to heel but said it would first look to impose tougher trade and currency sanctions to ensure the denuclearisation of the Korean peninsula. G20 protesters arrive in Hamburg. Credit:Andrew Meares Earlier this week, North Korea claimed its first successful launch of an intercontinental ballistic missile that could theoretically reach the US state of Alaska, and possible the northern city of Darwin - ratcheting up tensions in the region. Australian defence chiefs have, however, said there is little risk to Australia's north. Acting Australian Prime Minister Barnaby Joyce said that if "North Korea was to deliver a warhead into the United States of America then the ANZUS alliance would be called in", and suggested Australia could could look to join trade sanctions against Chinese companies that traded with North Korea. Riot police patrol ahead of the G20 in Hamburg. Credit:Andrew Meares

"What we are saying is that if there is an organisation that is trading with North Korea, that, that organisation - we have to look through the lens of this: Do you take this threat seriously? Do you want to - are you going to do anything about it? Are you just going to sit back and watch it? Ah, how far, how progress[ed] do you want North Korea to get in the capacity to put nuclear warhead into Darwin?" Mr Turnbull said before his departure that "only the strongest action from China can stop this escalation, this dangerous escalation by North Korea, absent military action". People take photos with police vehicles in Hamburg ahead of G20. Credit:Andrew Meares Labor deputy leader Tanya Plibersek chided Mr Joyce for being "gung-ho" and said a more "sober reflection would say that China has played an important role, both through diplomatic and economic means of putting pressure on North Korea not to engage in missile testing". At least 20,000 police will be in Hamburg to handle the rolling series of at least 30 scheduled protests that will see tens of thousands of people hit the streets.

Police vehicles in Hamburg ahead of the G20 meeting. Credit:Andrew Meares Loading As world leaders began to arrive on Thursday, a "G20: Welcome to Hell" protest march was due to take place, while the biggest action is expected for Saturday. Follow us on Facebook