Taoiseach Leo Varadkar has urged Northern Ireland's politicians to resolve their differences and restore powersharing as the Brexit talks enter their crucial stage.
Mr Varadkar has arrived in Northern Ireland for his first visit since becoming Taoiseach.
In a speech at Queen's University in Belfast, he warned that time is running out to try to achieve the best outcome for the island of Ireland after the UK leaves the EU.
He told an invited audience that "every single aspect of life in Northern Ireland could be affected by Brexit" and that it is "the challenge of this generation."
Mr Varadkar highlighted that the EU 27 would meet in October to decide whether enough progress had been made in the initial phase of negotiations - focused on the financial settlement, citizens' rights and the Irish border - to enable talks to proceed to the next phase.
He stressed the need for Northern Ireland's voice to be heard ahead of the crunch autumn decision.
"Today we need an answer to the question, of who do we - and others in Europe - talk to in Belfast?
"Who will speak for Northern Ireland and her 1.8 million people?
"Time is running out, and I fear there will be no extra time allowed."
He said those hard Brexiteers who advocated a hard border had to come up with proposals as to how that would work.
"They've already had 14 months to do so," he said.
He again insisted that the Irish Government will not design a hard border for Brexiteers.
Mr Varadkar said a meaningful solution could be the establishment of an EU-UK customs union.
"After all, we have one with Turkey. Surely we can have one with the United Kingdom?" he said.
The Taoiseach also suggested that if the UK does not want to stay in the single market, it could perhaps enter into a deep free trade agreement with the EU and rejoin the European Free Trade Association.
He said if this cannot be agreed now then perhaps there can be a period of transition during which the UK stays in the single market and customs union while the issues are worked out.
Mr Varadkar promised that the Government will do all it can in the Brexit negotiations to achieve the best outcomes for peace, freedom, rights and prosperity on the island of Ireland.
"At a time when Brexit threatens to drive a wedge between north and south we need to build more bridges and fewer borders.
"I promise I will play my part in helping to do exactly that," he added.
Mr Varadkar will later hold separate meetings with the leaders of Northern Ireland's main political parties.