In an interview with Fox News' Tucker Carlson broadcast Monday, President Donald Trump was asked about homelessness in American cities.

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

Official figures show that homelessness in general has decreased in the US since 2007, though it has spiked in some US cities.

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President Donald Trump sat down for an interview with Fox News, broadcast Monday, in which he said a 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 the host Tucker Carlson, who spoke warmly of Japanese cities like Tokyo and Osaka, which just hosted the two men for the G20 summit.

Carlson said Tokyo and Osaka didn't have "junkies" and were 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 had 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 from 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 last year found homelessness to be trending downward overall, with 647,258 Americans homeless in 2007 compared with the half a million more recently.

Homelessness is increasing in the cities named by Trump, however. Los Angeles' homeless population was recently found to have risen 16% year-on-year, to 36,300. An estimate in January found 8,011 homeless people in San Francisco, a 17% increase over the past two years.

Homelessness in those big cities has been linked to soaring property prices.

A report by the federal government in late 2018 found that 91,897 New Yorkers experienced homelessness at some point during the year, a 2% increase from the year before.