The call is set to come in around 4pm today.
The President allowed members of the media to witness the first part of the call and photographs from the Oval Office show the US President seated behind the Resolute Desk while speaking to Mr Varadkar.
The call comes as the POTUS has been given the green light to introduce his travel ban.
The ban has been reinstated until autumn.
Varadkar, 38, is Ireland's youngest prime minister. I know so many of them, too. The White House said later that Trump invited Varadkar to visit for St. Patrick's Day next year. "That was a great victory that you had", Trump said.
The "introductory" phone call between the two took place on Tuesday.
Other topics discussed included migration, Brexit, climate change, free trade, Irish inward investment in the United States, and the undocumented Irish.
The President asked for an update on the Northern Ireland peace process and the situation regarding border controls between the North and the Republic.
US President Donald Trump congratulated Varadkar on his "great victory"..
Mr. Varadkar said that he will raise issues such as climate change, LGBT rights, and immigrant rights on a future USA visit.
London fire manslaughter charges tipped
The speed at which the fire engulfed the 24-storey Grenfell Tower raised questions about the external cladding on the block. McCormack also repeated calls for anyone with information on who might have been in the tower to come forward.
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