President Donald Trump sat down for an interview with Fox News, broadcast Monday, where he claimed that the homelessness crisis in US cities began two years ago and was caused by “liberal elites.”

The remark – contradicted by official data – came in an interview with host Tucker Carlson, who spoke warmly of Japanese cities like Tokyo and Osaka, which has just hosted the two men for the G20 summit.

Carlson said Tokyo and Osaka don’t have “junkies” and are places where people don’t “go to the bathroom on the street.” He contrasted them to New York, San Francisco, and Los Angeles, which he said have a “major problem” with “filth.”

In response, Trump said:

"It's a phenomena that started two years ago. It's disgraceful.

"We're doing some other things that you probably noticed like some of the very important things that we're doing now. But we're looking at it very seriously because you can't do that.

"You can't have what's happening - where police officers are getting sick just by walking the beat. I mean, they're getting actually very sick, where people are getting sick, where the people living there living in hell, too.

"Some of them have mental problems where they don't even know they're living that way.

"In fact, perhaps they like living that way. They can't do that. We cannot ruin our cities.

"And you have people that work in those cities. They work in office buildings and to get into the building, they have to walk through a scene that nobody would have believed possible three years ago."

He went on to tie the problem to the "liberal establishment," echoing Fox News hosts who have attacked Democrat-run municipal authorities for homelessness in cities.

"And this is the liberal establishment. This is what I'm fighting," he added. "They - I don't know if they're afraid of votes. I don't know if they really believe that this should be taking place. But it's a terrible thing that's taking place."

He said went on to pledge that homelessness in cities would be "cleaned up."

"When we have leaders of the world coming in to see the president of the United States and they're riding down a highway, they can't be looking at that," he said.

"They can't be looking at scenes like you see in Los Angeles and San Francisco... So we're looking at it very seriously. We may intercede. We may do something to get that whole thing cleaned up." He did not provide details.

According to federal government data, the total number of homeless people increased slightly over the two years 2016 to 2018, with 552,830 homeless last year, and 549,428 homeless in 2016, despite a strong underlying economy.

But a Business Insider analysis shows that homelessness has gone down considerably in recent years, with 647,258 Americans homeless in 2007 compared with the half a million now.

In the cities named by Trump, homelessness is increasing. The number of people of people sleeping rough is up 16% year-on-year, to 36,300, in Los Angeles, and up 17% in San Francisco over the last two years, where 8,011 people were found to be homeless.

In LA, homelessness has been linked to soaring property prices, while in San Francisco it was linked to the tech industry boom.

91,897 New Yorkers experienced homelessness in 2018, a 2% increase, according to federal government figures.