US President Donald Trump has abruptly cancelled a planned meeting with Russian President Vladimir Putin in Argentina, citing Russia's treatment of Ukraine and casting new uncertainty over US-Russian ties.
Trump says he pulled out due to tensions over Russian forces opening fire on Ukrainian navy boats and then seizing them and their crew on Sunday near Crimea, which Russia annexed from Ukraine in 2014.
"Based on the fact that the ships and sailors have not been returned to Ukraine from Russia, I have decided it would be best for all parties concerned to cancel my previously scheduled meeting in Argentina with President Vladimir Putin," he wrote on Twitter.
"I look forward to a meaningful Summit again as soon as this situation is resolved!" Trump added, shortly after taking off for the weekend summit in Buenos Aires.
Trump's tweet from aboard Air Force One shortly after take-off from Washington on the way to Buenos Aires for a Group of 20 summit, was a sudden turnaround.
Roughly an hour earlier, he had told reporters he would probably meet with Putin at the summit and said it was "a very good time to have the meeting".
Trump had also said he would get a final report during the flight to Argentina on the tension in the region after Russia seized Ukrainian vessels near Crimea on Sunday.
White House spokeswoman Sarah Sanders told reporters on the presidential aircraft that Trump made the decision not to meet Putin after speaking with Secretary of State Mike Pompeo, White House chief of staff John Kelly and national security adviser John Bolton.
The decision appeared to catch the Kremlin by surprise. The Kremlin's spokesman said Moscow had no official information on Trump's decision, and that if true, Putin would have some extra time for a useful meeting at the G20 summit.
Differences over Ukraine, as well as Moscow's role in the civil war in Syria, have been an irritant in US-Russian relations for years.
Morrison hoping to talk to Trump
Meanwhile, Scott Morrison has flagged he could meet with Donald Trump at the G20 summit in Argentina, despite not being included on the US president's formal program.
"Watch this space, as he (Trump) would say," Mr Morrison told reporters in Canberra ahead of jetting off to Buenos Aires for the two-day gathering.
Trade tensions between the US and China, concern over the murder of Saudi journalist Jamal Khashoggi and calls to put climate action back on track form the background of the G20 summit in the Argentinian capital.
Mr Morrison will join Mr Trump and other world leaders in a series of sessions on Friday and Saturday (Argentina time) dealing with such issues as anti-corruption, education, jobs, climate and energy.
He will be accompanied by Finance Minister Mathias Cormann, after Treasurer Josh Frydenberg pulled out to deal with domestic political issues.
Many leaders will be seeking to talk to Saudi Crown Prince Mohammed bin Salman, who will be attending the summit, amid concerns about the murder of Khashoggi.
However, of greater interest will be a meeting between Mr Trump and Chinese President Xi Jinping and the potential signing of a trade deal between the US, Mexico and Canada.
Mr Morrison said in a statement he would seek a "constructive way forward" on global trade.
"A strong multilateral trading system with the World Trade Organisation at its' centre has helped underwrite regional and global economic stability and prosperity," he said.
"This is critically important to Australia as an open, trade-reliant economy - our continued growth and prosperity depends on it."
Ahead of the summit, International Monetary Fund boss Christine Lagarde warned against further trade barriers, including Mr Trump's proposed car tariffs to protect American auto jobs.
"We have had a good stretch of solid growth by historical standards, but now we are facing a period where significant risks are materialising and darker clouds are looming," she said.
"Rising trade barriers are ultimately self-defeating for all involved. Thus, it is imperative that all countries steer clear of new trade barriers, while reversing recent tariffs."
Prime Minister Scott Morrison is off to the G20. Source: AAP
UN Secretary-General Antonio Guterres, who is also attending the summit, told reporters the world needed "stepped-up global leadership".
"Strong economic growth, reduced inequality, and limiting carbon emissions are possible and compatible," he said.
"But we need greater ambition. We are in a race for our future. It's a race we can and simply must win."
The G20 includes Argentina, Australia, Brazil, Canada, China, Germany, France, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Turkey, United Kingdom, United States and the European Union.
