US President Donald Trump has ratcheted up his verbal assault on the media, describing it as "the enemy of the American people" in a tweet.

Shortly after landing at his holiday home in Florida - where he is spending a third consecutive weekend - the president lashed out at several news organisations.

"The FAKE NEWS media (failing @nytimes, @NBCNews, @ABC, @CBS, @CNN) is not my enemy, it is the enemy of the American People!" he wrote on Friday.

Trump had posted an earlier tweet that took aim at the New York Times, CNN, NBC "and many more" media organisations - and ended it with the exclamation "SICK!"

But he swiftly deleted that before tweeting the final version, adding two more "enemies" to his list.

Many US presidents have criticised the press in the past, but political analysts say Trump's language has more closely echoed that of authoritarian leaders.

Trump, who regularly accuses the media of overstating his problems, has also accused journalists of failing to show sufficient respect for his accomplishments - including in their coverage of a long-winded press conference on Thursday in which he voiced a litany of grievances against the industry.

Many journalists were taken aback by the extraordinarily combative press conference, which was described by some as bizarre, but Trump later echoed words of praise he got from one right-wing commentator and insisted it had been a bravura performance.

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The 70-year-old partly built his election campaign on criticising the press as biased.

Month of tumult

In four tumultuous weeks, Trump has seen his national security adviser ousted, a cabinet nominee withdraw, a centrepiece immigration policy fail in the courts and a tidal wave of damaging leaks.

Trump tried to put that first month of difficulties behind him as he pitched himself as a champion of US jobs and industry during a visit to Boeing in South Carolina.

Trump spent 16 minutes agonizing whether to include more organizations or "SICK!" in his revised tweet pic.twitter.com/z8t8h99HH7 — Brett LoGiurato (@BrettLoGiurato) February 17, 2017

He used the visit to publicly renew a campaign vow to champion jobs and industry.

"As your president, I'm going to do everything I can to unleash the power of the American spirit and to put our great people back to work," he said.

"This is our mantra, 'buy American and hire American.' We want products made in America, made by American hands," Trump added, pledging to wean the country off imports.

Although the unemployment rate is at a low five percent and wages are rising steadily, a triple whammy of deindustrialisation, globalisation and automation have hit the US heartland hard.