A June summit of European Union leaders is the "ultimate deadline" to make progress on issues related to Northern Ireland's border, French Foreign Minister Jean-Yves Le Drian said on Sunday.
"The June deadline is the deadline that must be seen as the ultimate deadline" to find a way to avoid a hard border between Ireland and Northern Ireland and allow progress in Brexit talks, Le Drian told reporters in Dublin.
Britain's Brexit minister David Davis in April told a British parliamentary committee that June was an "artificial deadline" on the issue.
On Sunday, British Prime Minister Theresa May said any deal must protect the United Kingdom's constitutional and economic integrity and honor the Northern Irish peace accords.
"This means there can be no hard border between Northern Ireland and Ireland, or between Northern Ireland and the rest of the UK," May wrote.
"Any agreements must create as little friction as possible for trade," she said, adding: "We must not constrain our ability to negotiate trade agreements with other countries around the world by being bound into a customs union."