The backstop will not be up for renegotiation at a meeting between the prime minister and taoiseach, the Irish government has insisted.
While the encounter between Boris Johnson and Leo Varadkar, which is set for early September, will focus on the Brexit impasse and Northern Ireland issues, Dublin was keen to stress that changes to the Withdrawal Agreement would not be countenanced.
Brussels and London remain at loggerheads over the prospect of fresh Brexit negotiations.
The UK Government has said any new negotiations must focus on developing an alternative to the Withdrawal Agreement.
EU leaders insist the deal cannot be reopened but will engage on potential amendments to the Political Declaration on the future relationship between the UK and the bloc.
Last week, Mr Varadkar said the invite to Mr Johnson to join him in Dublin for talks on Brexit and other issues had “no preconditions”.
A spokesman for the taoiseach said on Sunday: “The Taoiseach has invited the British Prime Minister to Dublin for talks on Northern Ireland and Brexit.
“Their offices are in contact to agree a date for these talks in the coming weeks.
“Such a meeting would give both sides an opportunity to gain a better understanding of their respective positions.
“As has repeatedly been made clear, the Withdrawal Agreement and the backstop are not up for negotiation.
“Any discussions on changes to the Political Declaration would occur between the UK and the EU.”
Mr Johnson has insisted a Brexit deal is only possible if the backstop is scrapped.