Sinn Féin president Mary Lou McDonald and DUP leader Arlene Foster have not been invited to the White House St Patrick's Day reception, but Gerry Adams and Ian Paisley jnr have.
The Irish Times has learned the leaders of the two main political parties in Northern Ireland have not received an invitation to the annual event, which takes place in the East Room of the White House on Thursday evening.
It is understood the decision was made because of the failure to have a functioning executive in Northern Ireland.
The decision breaches a long-standing tradition by the White House to invite the leaders of the two parties to the event, which is attended by political and civic leaders from both sides of the Border.
Ms McDonald is in the United States as part of a Sinn Féin delegation which includes Mr Adams and the party's deputy leader, Michelle O'Neill.
A Sinn Féin spokesman said the issue of invites to the reception was a matter for the White House.
Meanwhile, Taoiseach Leo Varadkar, also in the US, has delivered his strongest message yet on Brexit.
He said a hard border was being imposed “by a government in London” against the will of people in Northern Ireland, and confirmed the Irish Government would seek a special arrangement for the North in Brexit negotiations if necessary.
Special arrangement
Speaking during a keynote address at the South by South West festival in Austin, Texas, he said there was “no way” Ireland could countenance a hard border being enforced.
“Having reached the stage where we have peace and relative prosperity on our island we cannot risk going backwards . . . If we have to, we will have to press for a special arrangement for Northern Ireland, that will treat Northern Ireland some way differently.”
The European Union has said it would support special status for the North and allow it to remain part of the single market and the customs union.
This is a position supported by Sinn Féin but the DUP has strongly resisted such a move.
Mr Varadkar also took the opportunity to invite members of the the British cabinet, including foreign secretary Boris Johnson and Brexit secretary David Davis, to visit the Border, insisting it would be "helpful" to the current deliberations.
“There is a good opportunity for us to explain the issues that are unique to Ireland but as is always the case, and this is true for any politicians or anyone in any walk of life, you can read as many briefing documents as you like. Sometimes you need to see things with your own eyes and I think for that reason they would be very welcome to visit the Border and see it for themselves.”
The Taoiseach said Northern secretary Karen Bradley and a delegation of British politicians from the House of Lords and House of Commons had done so previously.
