Speaking with reporters alongside Taoiseach Leo Varadkar on Thursday, Trump said that he was in Scotland at the opening of his new golf club the day before the referendum, and that he'd stated his belief that Britain would vote to leave the European Union.
U.S. President Donald Trump will participate in a Shamrock Bowl event on March 14, where he will be presented with a vase full of Irish shamrocks by Ireland Taoiseach Leo Varadkar.
He also said another vote on Brexit would be unfair, and reiterated that he would like to see a USA trade deal with the United Kingdom after it leaves the EU.
"I will tell you, I'm surprised at how badly it has all gone from the standpoint of a negotiation".
On the prospect of another referendum, Mr Trump said: "I don't think another vote would be possible because it would be very unfair to the people that won".
Mr Trump also used Mr Varadkar's visit to the White House yesterday to warn Ireland and the EU the United States is "going to tariff a lot of their products coming in because the European Union treats us very, very unfairly".
He said he told Mr Trump there was an opportunity for an EU-US trade deal.
"I particularly want to thank you for your help with the plant in the west of Ireland where hundreds of jobs were threatened as a result of the Russian sanctions", he stated.
"We have a different opinion, president", said the Irish prime minister.
"We can do a very big trade deal with the United Kingdom".
Varadkar and his partner are in Washington as part of an annual trip ahead of St. Patrick's Day.
The most concerning element for Ireland, Varadkar said, is that Brexit should not cause any problems in Northern Ireland, which voted to stay in the EU. "I regret Brexit's happening".
Varadkar said he appreciates what the president has done for his country economically.
Parliament has twice now rejected the withdrawal agreement May negotiated with the European Union, though it voted this week against leaving without a deal in place.
"I predicted it was going to happen, and I was right. I think it'll be a few years until the United Kingdom sorts itself out, but in the meantime the European Union is available to talk trade with the USA".
Trump spoke hours before British lawmakers voted to delay Brexit for at least three months.
Mr Trump has said he will be visiting the Republic of Ireland at some point this year.
Varadkar continued, "We shouldn't have a hard border, or anything to disrupt the peace process".