DAVOS, Switzerland (Reuters) - U.S. President Donald Trump called climate activists like Greta Thunberg “prophets of doom” at the World Economic Forum on Tuesday. By Wednesday he was lamenting not having watched the teenage activist’s speech.

The gentler tone, along with a promise to join a plan to plant one trillion trees, hinted at a different approach from the U.S. president, who in the past has dismissed climate change as “fake news” and told Thunberg she needs “anger management”.

Either way, the first two days of the annual Davos gathering were dominated by the back-and-forth between the 73-year-old former businessman and the 17-year-old campaigner, with corporate leaders caught in the middle, concerned that as well as words, there was a need for concrete decisions.

Thunberg doubled down at Davos.

“Our house is still on fire,” the Swede said, decrying the “empty words and promises” of leaders and their message that children -- millions of whom have joined Thunberg’s Friday protests around the world -- should not worry.

“Your inaction is fuelling the flames,” she said.

ENTER THE GREEN PRINCE

On Wednesday, she met Britain’s Prince Charles, 71, a life-long environmentalist who tries to keep out of politics.

“Everything I have tried to do, and urge, over the past fifty years has been done with our children and grandchildren in mind,” Charles said shortly before sitting down with Thunberg.

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He said he did not want to be accused by his descendants of doing nothing “except prevaricate and deny the problem”.

“Now, of course, they are accusing us of exactly that.”

Trump and the British heir to the throne did not cross paths, but as he left the mountain resort, Trump told reporters he would have liked to have heard Thunberg speak.

Business leaders suggested Trump had been listening. Asked if he had convinced Trump to join the trillion trees initiative, Salesforce chief executive Marc Benioff paused and smiled before telling Reuters “many people” were involved.

And Joe Kaeser, the chief executive of German giant Siemens, told Reuters he had advised Trump to listen to young activists. “We have to sit together and involve them in dialogue,” he said he had told the U.S. president.

Asked by reporters if he still thought climate change was a hoax, Trump responded: “No, not at all.”

But he said Thunberg should shift her attention away from the United States to focus on other, more polluted countries.

“You have another continent where the fumes are rising at levels that you can’t believe ... I think Greta ought to focus on those places,” he said.

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Other leaders sought to draw a middle ground between Trump and Thunberg. French finance minister Bruno Le Maire said the Europeans were leading with a different approach.

“There exists a third way between Donald Trump and Greta Thunberg,” he told reporters.

“There’s no need to fall into extremes, between those who say either that there is no problem with global warming or those who lament that nothing has been done to combat it, because it’s not true – there are things that have been done.”

Mark Carney, the outgoing head of the Bank of England who will shortly become a United Nations’ envoy for climate policy, praised Thunberg for raising awareness of climate change.

“There are those who will be out front in the transition and those who lag. And that’s different than a binary green-good, everything else brown-bad,” he said. “There should be fifty shades of green, if not more.”