Taoiseach Micheál Martin has had his first call with Britain's new prime minister Liz Truss on Friday afternoon following her appointment on Tuesday.
Mr Martin offered his sympathies to Ms Truss after news of the death of Britain's Queen Elizabeth II on Thursday.
The queen's death came just two days after inviting the new prime minister to form a government at her estate in Balmoral, Scotland after Boris Johnson formally tendered his resignation to the British monarch.
In a statement, the Department of the Taoiseach confirmed Mr Martin and Ms Truss reflected on the queen's State visit to Ireland in 2011 "and its contribution to advancing reconciliation and relations on these islands".
The Taoiseach also congratulated Ms Truss on her appointment, adding that he looks forward to "working constructively" with her.
"They discussed the illegal Russian invasion of Ukraine, their support for Ukraine, and recognised the substantive EU-UK cooperation as part of the global response", the statement said, adding they also exchanged views on common challenges including soaring energy prices and the rising cost of living.
On the matter of the Northern Ireland Protocol, the two leaders "agreed to keep in close contact in the weeks ahead".
During her time as Britain's foreign secretary, Ms Truss tabled the controversial Northern Ireland Protocol Bill which seeks to row back on trade agreements the UK made with the European Union during Brexit negotiations.