US President Donald Trump has said America has "much to learn" from Australia's controversial policies to deter illegal immigrants.
US President Donald Trump and Australian Prime Minister Scott Morrison will not be lacking a conversation starter when they sit down for dinner at the G20 in Osaka, Japan.
Mr Trump took to Twitter aboard Air Force One on his flight to Japan on Wednesday to post four confronting anti-illegal immigration posters created by the Australian government in 2014.
Mr Morrison was Australia's immigration minister at the time.
The posters are no longer used, but that did not stop Mr Trump who is heading into the 2020 presidential election with security on the Mexico-US border one of his top issues to win votes.
"These flyers depict Australia's policy on Illegal Immigration," Mr Trump wrote.
"Much can be learned!"
One of the posters is a photo of a boat on a rough, open ocean with the warning: "NO WAY. YOU WILL NOT MAKE AUSTRALIA HOME".
Another says: "Australia's borders are closed to illegal immigration".
Australia’s policy of detaining refugees and asylum seekers in offshore detention centres has been widely condemned by human rights advocates.
A UN human rights officials recently urged Australia to provide immediate medical aid to more than 800 asylum seekers and migrants being held offshore after a spate of suicide attempts following the May election result.
Most recently, Ravinder Singh, an Indian asylum seeker, locked himself in his room and set it on fire at Manus Island immigration detention centre.
His friend and a fellow detainee told SBS Punjabi he had been struggling with back and shoulder pain for months and was distressed at not receiving proper medical care.
According to the Refugee Action Coalition, there have been nearly 100 cases of self-harm on Manus Island, involving more than 62 asylum seekers and refugees.
Under hardline policies, Australia turns back anyone trying to arrive in the country by the sea - including refugees fleeing wars and unrest as far afield as Sudan and Iranian Kurdistan.
Advocacy group Refugee Action Coalition said on Monday mental health had reached a "crisis point", after another separate report of self-harm.
Greens Immigration spokesperson Senator Nick McKim on Thursday slammed the president's tweet.
"We should be horrified that one of our most shameful policies is being applauded by one of the world's cruellest leaders," the senator said.
Mr Trump calls the border crossings a national emergency and has requested $US4.5 billion in emergency aid to help law enforcement address "the historic surge in large migrant groups arriving at our southern border".
Mr Morrison will be the first world leader to meet with Mr Trump at the G20. They will have dinner on Thursday evening.
On Friday Mr Trump will meet with Japanese Prime Minister Shinzo Abe, Indian Prime Minister Narendra Modi, German Chancellor Angela Merkel and Russian President Vladmir Putin.
On Saturday he will hold the much-anticipated meeting with Chinese President Xi Jinping.
Mr Morrison backed the controversial posters in 2014, describing them as part of a "targeted campaign".
"This will complement the offshore communications campaign about the government's strong border protection policies which comprises the overwhelming allocation of resources in which messaging is delivered directly through transit and source countries,'' a spokesman for the minister said at the time.
Senator McKim said Mr Trump's tweet "applauding Australia's immigration policy tells us all we need to know about its cruelty".
"This is mortifying in the extreme, but comes as no surprise after neo-nazi groups in Europe adopted and embraced the same propaganda last year," the senator said.
"Trump is taking a leaf out of Australia's book, and just as on Manus Island and Nauru it is innocent people and children who are paying the price with their lives and freedom."