President Donald Trump insisted Friday that the United States paid North Korea nothing for the release of Otto Warmbier, a young American student who fell into a coma after allegedly being tortured in the totalitarian country.

On Thursday, The Washington Post quoted unidentified sources as saying that a US official was made to sign a pledge to pay $2 million in medical costs before being allowed to fly Warmbier back home from Pyongyang in 2017.

The envoy signed the pledge on instructions from Trump, the Post reported.

But in a tweet Friday, Trump said: “No money was paid to North Korea for Otto Warmbier, not two Million Dollars, not anything else.”

He then wrote, without saying where the quote came from: “President Donald J. Trump is the greatest hostage negotiator that I know of in the history of the United States. 20 hostages, many in impossible circumstances, have been released in last two years. No money was paid.” Cheif (sic) Hostage Negotiator, USA!”

Warmbier, a University of Virginia student, was imprisoned after being accused of taking down a propaganda poster in his hotel during a trip to North Korea.

Doctors said he suffered severe brain damage while in North Korean detention, fell into a coma and died days after arriving back in the United States.

North Korea denied claims by the Warmbier family that he had been tortured, saying he had contracted botulism.

A coroner who examined Warmbier’s body said: “We don’t know what happened to him. That’s the bottom line”.

Trump has made rapprochement with North Korea one of his signature policies and he has held two summits with North Korean leader Kim Jong Un.

At their last meeting in Hanoi in February, Trump said he accepted Kim’s claim not to have known what had happened to Warmbier in prison, despite the case being extraordinarily sensitive.

“I will take him at his word,” Trump said.

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