Donald Trump suggested dramatic constitutional changes and claimed to be “the chosen one”, on a day when he lurched from insulting allies to claiming American Jews who vote Democrat are being disloyal to a foreign country.

In a day extraordinary even by his standards, the US president delivered a remarkable series of statements, veering from quasi-authoritarian proposals for serving more than two terms to apparently humorous suggestions that he should be awarded the Medal of Honor – despite his repeated draft deferrals.

Along the way he managed to call the prime minister of Denmark – a key Nato ally – “nasty” for refusing to discuss selling him Greenland, and approvingly retweeted a description of himself as “King of Israel” and “the second coming of God”, adding: “Wow!” He also:

unveiled new rules that allow the US government to detain migrant families indefinitely while their asylum cases are judged

blamed Barack Obama for his own family separation policy

boasted about how much he was loved by survivors of mass shootings

insisted that the second amendment, guaranteeing gun ownership, would “stay strong”

said Russian president Vladimir Putin had “made a living” of outsmarting Obama

railed against the “fake news’, singling out NBS, the New York Times and CNN

touted a private drug for preventing suicide

and threatened to release European ISIS prisoners back into their own countries.

Mr Trump also addressed the state of the economy, insisting it was in good shape and in no danger of falling into recession. And he defended his trade war with China, suggesting he had the backing of a higher power.

Looking up to the sky, with his palms open, he declared: “I am the chosen one!

Trump says Democrat voters are 'disloyal to Israel'

“Somebody had to do it. So I am taking on China. I’m taking on China on trade. And you know what? We’re winning.”

Talk of a possible recession is thought to have unsettled the president, whose boasts about the economy have been a key feature of his presidency – and are seen as key to his re-election hopes next year.

He once again attacked the chairman of the Federal Reserve, Jerome Powell, summoning up a film reference as he said he had raised interest rates “too fast, too furious”.

And he pushed back on the idea of a payroll tax cut, which he said only yesterday had been under discussion. “I’m not looking at a tax cut right now. We don’t need it. We have a strong economy.”

Asked why he had cancelled a trip to Denmark, he said it was because its prime minister, Mette Frederiksen, had been “nasty” about his surprise wish to buy Greenland.

He said: “The prime minister used a terrible word when describing something we’ve been talking about for years with our country. President Truman said, ‘what about Greenland?’, and he talked about it very openly and it was a big deal at the time. And I brought it up again and it was discussed many other times.

“And I thought it was not a nice statement, the way she blew me off, because she’s blowing off the United States. And we’ve done a lot for Denmark … She said ‘absurd’ – that’s not the right word to use.”

'It's frankly ridiculous' Donald Trump says US is considering abolishing birthright citizenship

Denmark is a founding member of NATO and contributed troops towards the US-invasion of Afghanistan in 2001. Forty-three Danes lost their lives in the conflict.

A day after saying that American Jews who vote Democrat were showing “great disloyalty”, the president explained what or whom he thought they were being disloyal to – Israel.

Apparently unaware that accusing Jews of having split loyalties to their own countries and to Israel is a long-standing antisemitic trope, he said: “In my opinion, if you vote for a Democrat, you are being very disloyal to Jewish people and you are being very disloyal to Israel. And only weak people would say anything other than that.”

His administration also unveiled a new rule that allows migrant families to be detained indefinitely while their asylum cases are judged, overturning an agreement that children should not be held in immigration cells for more than 20 days and which guarantees minimum levels of care.

On the birthright issue, Mr Trump said he was looking at using an executive order to end the right of citizenship to children born in the United States.

He said: “We’re looking at that very seriously, birthright citizenship, where you have a baby on our land, you walk over the border, have a baby – congratulations, the baby is now a U.S. citizen. ... It’s frankly ridiculous.”

Bernie Sanders was among those who hit back at the president over his comments on Jews. The Democratic presidential hopeful said: “My message to Trump: I am a proud Jewish person and I have no concerns about voting Democratic.”