The Irish border will be a special case in the Brexit negotiations, French president Francois Hollande has claimed.
Mr Hollande, in Dublin for talks with Taoiseach Enda Kenny, called on Britain to begin its separation from the European Union sooner rather than later, and for the discussions to be as short as possible.
Amid concerns the open border between Northern Ireland and the Republic could be replaced with customs and immigration checks, the French leader said he understood the concerns about the peace process.
"I do recognise there is a special situation here for Ireland," he added in a Press conference.
"It's a special situation and it has to be found a special place in the negotiations."
Mr Hollande's trip to Dublin was arranged before last Friday's Bastille Day atrocity in Nice.
Eighty-four people were killed when Tunisian Mohamed Lahouaiyej Bouhlel drove a truck into crowds enjoying celebrations and fireworks over the Promenade des Anglais. Another 15 people remain critically ill in hospitals.
On the ramifications of Brexit for the soft border between Northern Ireland and the South, the Taoiseach reiterated that the UK-Ireland Common Travel Area and freedom of movement should remain.
"We do not favour a hard border," he said. "Obviously, we do not want to see a European border from Dundalk to Derry - that would not be acceptable. We'd be vigilant with people moving through who might ... be involved in terrorist activities."
Mr Kenny added that the French leader was aware of the importance of the crucial role the EU played in cementing the peace process.
"Europe has contributed greatly to the support of the Good Friday Agreement in putting that fragile peace together," the Taoiseach explained. "We see, as a country with a land border here, that this peace process is absolutely essential."
Later, following talks with Prime Minister Theresa May in Paris, Mr Hollande warned that Britain would not remain in the single market unless it accepted freedom of movement.
The French president said the thorny issue of migration would be the "most crucial point" of the UK's negotiations to leave the bloc, but indicated he would not agree to major concessions.
After talks at the Elysee Palace, the Prime Minister insisted that the Government would deliver on voters' demands for "some controls" on movement between countries.
Discussions continued over a dinner of lobster, veal and vanilla mousse.
Mr Hollande urged Britain not to delay triggering the Article 50 process of negotiations to pull the country out of the bloc, insisting: "the sooner, the better."
Asked about Britain's future in the single market, Mr Hollande replied: "It's the most crucial point. That's the point that will be the subject of the negotiation.
"It will be a choice facing the UK - remain in the single market and then assume the free movement that goes with it, or to have another status. That will be the subject of the negotiation."
Mrs May said the referendum result had been a "very clear message that we should introduce some controls to the movement of individuals from the countries of the European Union into the UK".
"Obviously, looking at that issue will be part of the negotiations," she added.
"I'm clear that the Government should deliver and will deliver on that for the British people, but we also want to get the right deal on the trade in goods and services, and I think this is important economically, not just for the UK, but for other countries within the European Union as well."