Trump said Brexit was "tearing countries apart" and added that he was surprised "how badly" it has gone since the UK's referendum on leaving the EU.
President Trump and first lady Melania Trump welcome Irish Prime Minister Leo Varadkar at the South Portico as he arrives at the White House on Thursday. "But I think it could have been negotiated in a different manner".
He said: "I'm surprised at how badly it's all gone from the standpoint of a negotiation".
Mr Varadkar replied: "We have a different opinion, Mr President".
Gardiner rejects Irish concerns about the border and said the issue has been used as a "battering ram" by European Union leadership keen to make Britain a cautionary example to other member states flirting with an exit. "And with the help of the administration, we were able to save those jobs, so thank you very much for that".
Mr Trump, who was hosting Mr Varadkar for the annual St Patrick's Day visit to Washington, had earlier taken to Twitter to to express his hopes for a future working relationship with Britain. "I regret Brexit's happening". "I hate to see everything being ripped apart right now".
Mr Trump has said he will be visiting the Republic of Ireland at some point this year. "I predicted it was going to happen".
"We’re not English. We’re Scouse!" - Liverpool fans respond to owner
English teams used to rule the Champions League in terms of how many proceeded to the quarters and semis of the competition. A draw will also be made to determine which team will be the "home" team in the final .
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.
Mr Varadkar also said Ireland wanted frictionless trade with the United Kingdom and he believed in free trade, and while it may be years before the United Kingdom "sorted itself out", the European Union was "available to talk trade with the US".
She told BBC News NI that she would "very much" like to se the USA president visit Northern Ireland. "He has consistently emphasized Brexit as a prerequisite for a new U.S. -U.K. free trade agreement, and administration officials and members of Congress have been working diligently to prepare for such an agreement", Gardiner, director of the Margaret Thatcher Center for Freedom at The Heritage Foundation, tells VOA News.
Turning to Mr Varadkar, he said: "Leo, I'm sure you agree on that". He said: "If they don't talk to us, we're going to do something pretty severe economically".
"We shouldn't have a hard border or anything to obstruct the peace process. There's 500 million of us, only 60 million of them".
Mr Trump was due to visit the Republic of Ireland previous year, but it was cancelled for "scheduling reasons".