DUBL:IN — A failure by Britain and the European Union to reach a post-Brexit trade deal by the end-of-year deadline would pose an "existential threat" to Ireland, Prime Minister Leo Varadkar said Friday.

"We have to be realistic about the dangers," the Irish leader said in a speech in Dublin as Britain leaves the EU after 47 years.

"A failure to secure a trade deal would be a major threat, and an existential threat to our economy in 2021, so we do need that deal."

Britain will continue following EU rules on trade and other issues during an 11-month transition period that the sides have set aside to decide their future ties.

London has until July to ask for an extension — something Johnson has vowed not to do despite warnings that such talks usually take more time.

Ireland shares a border with Britain's Northern Ireland and will be directly impacted if there is no new trade deal by the end of the year.

It wants London and Brussels to reach as broad a free-trade agreement as possible. But this would require Britain to continue following many of EU's rules.

Johnson has said he wants Britain to set its own standards and regulations.

"We know it's going to be a pretty rocky couple of months," Varadkar told reporters.

"We want free trade with the UK with no tariffs, no taxes, no quotas and as little bureaucracy and as few checks as possible," he said.

"But no matter what happens, there will be bureaucracy and there will be checks, because things cannot be as they were before."

Varadkar called Brexit a day of great sadness that also showed the benefits of single European membership.

He also thanked EU leaders for supporting Ireland in the negotiations that allowed Britain to finally leave after three delays.

"The UK leaving is not a cause of celebration for us. There will be no issuing of commemorative coins for this event," he said in reference to the 50-pence one issued by Johnson's government.

"But we do celebrate the solidarity that has been shown by EU partners, and we say thank you to our fellow Europeans," he said.

"United we stand, divided we fall." — AFP