And then, of course, he commented at length.
"Thanks to the Vice President and his sister for a lovely morning at his home". "I regret that Brexit's happening".
For Irish leaders, even a modern figure such as the young, gay, mixed-race Varadkar, the event reinforces historical bonds that translate to tourism, business partnerships and other boons of shared history and language.
After Brexit, "we can do a very big trade deal with the United Kingdom", noted Trump.
Bilateral relations and the Irish undocumented immigrants in the USA were on the agenda for Mr Varadkar's Oval Office meeting with Mr Trump, but Brexit dominated their talks.
Varadkar and his husband, Matt Barrett, joined Vice President Mike Pence at the Naval Observatory for a breakfast earlier on Thursday.
Thursday's events carried on despite awkward timing.
"And I don't believe my country is the only one in the world where this story is possible". "There is every expectation in Washington that a U.S. -U.K. trade deal could be in place by the end of 2019 if Brexit goes forward this month and Britain successfully leaves the Customs Union". "The potential is unlimited!"
The Irish PM said the most pressing issue facing his country was how to settle questions about the future of the border between Ireland, an European Union member, and Northern Ireland, which won't be.
"I think that the relationship between Ireland and the United States is long-lasting - it's strong", Varadkar told The Washington Post in an interview on Wednesday.
The president said he had advised British Prime Minister Theresa May how to negotiate her country's divorce from the European Union, but "she didn't listen to that".
After he met Pence at his home past year, Varadkar told Irish reporters that the two discussed LGBT issues and that the vice-president told the Irish leader that his partner would be welcome at his home. "I predicted it was going to happen". "And I was standing out on Turnberry, and we had a press conference, and people were screaming".
"It is really great to have the prime minister of Ireland with us", Trump said, before stating that he's becoming "fast friends" with the Taoiseach.
The visit and the news conference were the day after the June 23 Brexit vote, not the day before. I think it could have been negotiated in a different manner, frankly.
That's a subtweet if I've ever seen one. MPs are set to vote on Thursday evening on whether to request a delay until at least June.
The exchange of views Trump is referring to took place in a meeting last summer, with May later saying that his advice was to sue the EU.
Pence glossed over the Brexit disagreement as he welcomed Varadkar for the breakfast, and grew nostalgic as he recounted his grandfather's emigration from Ireland and his own affection for the country. Pence attempted the Irish leader's formal title, calling him "Taoiseach Varadkar". Trump gave it a try, too, and got pretty close, at the final theatrical rite of the Irish visit - the presentation of a crystal bowl of shamrocks.
He said: "I know he is a supporter of Brexit and I am not".
Today the Taoiseach will leave Washington and travel to Chicago to meet emigrant support groups. He said: "If they don't talk to us, we're going to do something pretty severe economically". But it will all work out. "Everything does", he said.