Trump talks up US, hits at climate 'doom prophets'

US President Donald Trump lavished praise on the success of his presidency in his speech at the 50th World Economic Forum on Tuesday while lashing out at young climate activists.

In the speech, Trump gave a long list of the achievements during his three years as US president in everything from creating jobs, reducing unemployment and raising workers' wages to cutting taxes and regulations, boosting the stock market and securing trade deals, including the phase one trade agreement with China concluded last week.

"I'm proud to declare that the United States is in the midst of an economic boom the likes of which the world has never seen before," Trump said, echoing his messages on his 2020 presidential campaign trail.

It was Trump's second speech in the Davos forum. At the first one in 2018, he preached his America First policy. Trump did not mention the words "America First" on Tuesday, but the theme permeated his 30-minute speech.

In the speech, Trump described the two trade deals the US concluded last week with China and with Mexico and Canada as the "two biggest trade deals ever made".

Kenneth Rogoff, a professor of economics at Harvard University and a former chief economist at the International Monetary Fund, said Trump's trade policy is disruptive to the global economy. He was surprised that there are people saying things are better now.

"I would say when you hit your head against the wall and you stop hitting your head, it feels better. So certainly the trade policy is enormously disruptive, and I think all the claims that they (tariffs) have been wonderful to the US economy are misguided," Rogoff said.

He said tariffs have always been popular with the US public, and it is politically popular in the short run, but it's very damaging to the economy.

Bernie Sanders, a US Democratic presidential candidate, criticized Trump for claiming "America's extraordinary prosperity" in Davos.

"Meanwhile, income and wealth inequality explodes, half our people live paycheck to paycheck, and more than 500,000 are homeless," he said in a tweet.

While the theme of this year's World Economic Forum focuses heavily on the environment and climate change, Trump lashed out at young climate activists represented by Swedish girl Greta Thunberg.

"We must reject the perennial prophets of doom and their predictions of the apocalypse," Trump said, adding that "they are the heirs of yesterday's foolish fortunetellers".