Caitriona Perry, the Washington correspondent for Irish public service broadcaster RTÉ, was part of the press group observing the US president’s call with Leo Varadkar.
Trump could be heard saying “We have a lot of your Irish press watching us right now.”
“We have all of this Irish, beautiful Irish press. Where are you from? Come here, come here...”
Perry approached before quickly retreating again as Trump continued: “She has a nice smile on her face so I bet she treats you well.”
Perry described the moment as “bizarre”, and it left many deeply uncomfortable.
Trump was actually supposed to be congratulating Varadkar on his “great victory”, after he was voted Irish PM.
At 38, he is the country’s youngest ever PM, as well as its first gay leader.