The call is set to come in around 4pm today.
Trump made the phone call with media present and was photographed behind his desk in the Oval Office.
The call comes as the POTUS has been given the green light to introduce his travel ban.
The ban has been reinstated until autumn.
Since his confirmation as Taoiseach he has spoken to the French President Emmanuel Macron, the German Chancellor Angela Merkel and the Indian Prime Minister Narendra Modi. I know so many of them, I feel I know all of them.
Trump was calling Varadkar to congratulate him on the "great victory" in the recent election.
The call took place at 11.15 a.m.in Washington, 4.15 p.m.in Dublin.
The President asked for an update on the Northern Ireland peace process and the situation regarding border controls between the North and the Republic.
"I will not, of course, rescind that invitation", he said, adding that to do so would be "inappropriate" and would create a "diplomatic incident".
"I will absolutely include in those meetings discussions of the issues...whether it is climate change, human rights, LGBT rights, and the need to respect Muslim people, whether they are citizens of our country, or another country".