The president said: 'I'm surprised at how badly it's all gone from the standpoint of a negotiation.
"I gave the prime minister my ideas on how to negotiate it", he said at the White House during an appearance with Irish Prime Minister Leo Varadkar.
"The president, who described Brexit as a" attractive, lovely thing" during a visit to Scotland in June 2016, said the UK's divorce from the European Union is "tearing apart" Britain and other member states which he believes is "a shame".
"I'd like to see that whole situation with Brexit work out", Trump added. "I don't think another vote would be possible because it would be very unfair to the people that won", Trump said.
"We have a different opinion, president", said the Irish prime minister.
During the annual event, the Taoiseach presented the United States president with a bowl of shamrock to mark his St Patrick's visit to Washington DC.
But despite criticising Mrs May's approach at the negotiating table, Mr Trump reiterated his desire for a strong UK-US trade deal.
However, he later became critical of May's Brexit proposals; after European leaders endorsed her blueprint at a summit last November, he said the deal could disrupt the UK-US trade.More news: Europa League draw: Arsenal in nightmare quarter-final
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Leo Varadkar also thanked President Trump for his support of a new E3 visa programme which, if passed by Congress, would benefit Irish citizens who wish to work in the US.
"It's an enormous pleasure for Ireland, a small country, to have this annual meeting on account of St. Patrick's Day and to have a chance to make even closer and tighter the bonds between the United States and Ireland", Varadkar told Trump.
"I think it'll be a few years until the United Kingdom sorts itself out", predicted Varadkar.
He was referring to the cardiologist's time working in a hospital in the city as he welcomed Mr Barrett and Mr Varadkar to the US Naval Observatory residence. The president said he and Varadkar discussed the issue during their Oval Office meeting.
The British parliament on Tuesday overwhelmingly rejected Prime Minister Theresa May's Brexit deal, throwing the country's Brexit process into further chaos.
Pence tweeted that he was honored to host Varadkar at his home.
Varadkar, who was Ireland's health minister at the time, publicly announced his sexual orientation in a radio interview earlier that year, describing it as "part of my character, I suppose".