Taoiseach Leo Varadkar has said it is "only a matter of time" before same-sex marriage is introduced in Northern Ireland, as he attended a gay Pride event in Belfast.
He said he was attending the event to express solidarity and support for individual freedom and equality.
The North is the only part of the British Isles where same-sex marriage remains outlawed after the Republic voted to change the law in a watershed 2015 referendum.
Mr Varadkar said: "It is of course a decision for the Northern Ireland Assembly, but I am confident that like other western European countries they will make that decision in due course."
Police Service of Northern Ireland and Garda officers also joined Mr Varadkar at the event, arriving in a PSNI Land Rover.
For the first time uniformed officers will march in the Pride parade through the city centre.
Assistant Chief Constable Barbara Gray said the PSNI's participation in the breakfast and parade "is about inclusion and representation".
"We represent all sections of society. Members of the LGBT community are a marginalised community in Northern Ireland," she said.
Mrs Gray added that the PSNI's presence at the events might encourage victims of hate crime to come forward and report them.
Up to 8,000 people are due to parade through Belfast city centre later.
Same-sex marriage has been one of the sticking points preventing the return of a devolved powersharing administration at Stormont, with Sinn Fein demanding the Democratic Unionists (DUP) stop blocking changes to the law.
The DUP, Prime Minister Theresa May's partner in government, has used a controversial Stormont voting mechanism to prevent the legalisation of same-sex marriage, despite most Assembly members supporting the move at the last vote.
The DUP rejects any suggestion it is homophobic, insisting it is protecting the "traditional" definition of marriage, and has called for tolerance of what are increasingly minority views.
It does not have enough members in the new Assembly to veto an equal marriage vote on its own, but there is no immediate prospect of the deeply divided administration being restored.
Mr Varadkar is not staying for the Pride parade because of other commitments.
A total of 8,000 people are expected to march from Custom House Square in the city centre and about 15,000 additional supporters are anticipated, said the Parades Commission, which rules on marches. Sixty bands are due to take part.
A rainbow Pride flag has been raised at a UK Government building at Stormont for the first time.
The flag was raised beside Stormont House on Friday morning to mark the Pride festival.
LGBT+ Conservatives patron, Stuart Andrew MP, will take part in the Pride march along with thousands of local demonstrators.