And Prime Minister Malcolm Turnbull has suggested an Australia-EU free trade agreement could be struck as soon as the end of 2019.

In a joint media statement at the Elysée Palace on Saturday evening, Mr Macron and Prime Minister Malcolm Turnbull noted how Australia's support for free trade and its commitment to the Paris climate change agreement was drawing the nation closer to France and the other nations of Europe, even as the United States under Donald Trump pulls away.

Mr Turnbull and his wife Lucy had earlier joined Mr Macron and his wife Brigitte on the French leader's private plane after the G20 summit in Hamburg ended.

The Prime Minister's flight on the president's plane is believed to be the first time ever another world leader has flown on the French president's plane.

President Macron said the decision to choose French company DCNS was an honour for French industry and "we will do our utmost and everything necessary to meet the requirements of the contract.

The French leader also thanked Australia for its commitment to the Paris climate agreement, while Mr Turnbull said the submarines - which are not due to enter service until the 2030s - was the "largest and most ambitious military project in Australia's history".

"The future submarine project is a generational, a multi-generational project. It is a national enterprise. And it is one where we are working together, our two nations side-by-side as our forebears did so long ago," Mr Turnbull said.

Mr Turnbull said he and Mr Macron had met with European Council president Donald Tusk and European Commission president Jean-Claude Juncker to discuss Australia's push to strike a free trade agreement with Europe.

"Our commitment and theirs, I believe, is to do everything we can to ensure that we can get that free trade agreement negotiated over the next 18 months. We would like to get it agreed by 2019. That is a realistic but ambitious objective," the prime minister said.

Mr Turnbull and Mr Macron had left behind a G20 divided over climate change and unable to agree on new measures in response to North Korea's provocative intercontinental ballistic missile test, and appeared at the Elysée Palace late on Saturday evening.

On climate change and to a lesser extent trade, Mr Trump was isolated on the international stage, as the other 19 G20 nations issued a statement declaring their commitment to the Paris climate change agreement was "irreversible".

The communique included a controversial paragraph which noted the US "will immediately cease the implementation of its current nationally-determined contribution" to emissions reductions and in which it promised to "work closely with other countries to help them access and use fossil fuels more cleanly".

On trade, another sticking point, the G20 leaders agreed they would "fight protectionism" and Dr Merkel said trade had been a difficult subject to negotiate the "America First" president, while she also condemned North Korea's recent actions.

North Korea's most recent, and successful, test firing of an ICBM that could theoretically reach Darwin featured prominently in discussions at the G20 meeting.

China and Russia objected to a joint statement being issued by the G20 on North Korea and to tougher sanctions, arguing the summit was an economic forum, though the United States, Japan and South Korea jointly pledged tougher sanctions.

On counter-terrorism and digital encryption, Mr Turnbull had a win, after helping to personally draft a section of the leaders' final statement.

The paragraph promised, in part, that "in line with the expectations of our peoples, we also encourage collaboration with industry to provide lawful and non-arbitrary access to available information where access is necessary for the protection of national security against terrorist threats".

This pledge represented some progress towards achieving what Mr Turnbull - and other world leaders including German Chancellor Angela Merkel and British Prime Minister Theresa May - have stated is the need to crack down on the so-called "ungoverned spaces" online that have been used by terrorists to organise and plot terror attacks.

Mr Turnbull and President Trump had three impromptu discussions during the G20 summit, while Mr Turnbull also had "pull asides" and bilaterals with world leaders from China, South Korea, Indonesia, Vietnam and other nations.

In his meeting with South Korean president Moon Jae-in, Mr Turnbull pledged Australia's commitment to ensure peace on the Korean peninsula

"Of course as always you have our absolute support in your efforts to ensure peace and stability is restored on the Korean peninsula," Mr Turnbull said.

In his discussion with Prime Minster Nguyen Xuan Phuc, the Vietnamese leader raised concerns about five local councils in Australia that reportedly support the flying of the "yellow" flag, which was the flag of the former government of South Vietnam.

Mr Nguyen asked Mr Turnbull to exert his influence and stop the practice.