THE Irish premier has said he is confident an agreement between the UK and EU over Brexit can be reached by tonight.

Leo Varadkar said he had spoken to Prime Minister Boris Johnson earlier this morning and he is optimistic progress is being made and that a deal could be ratified at the European Council summit on tomorrow or Friday.

His comments came as Brexit Secretary Stephen Barclay confirmed Johnson would write to the EU to request an extension if no deal was agreed by Saturday evening.

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The Taoiseach said: "There is a pathway to a possible deal but there are many issues that still need to be resolved, particularly around the consent mechanism and issues around customs and VAT.

"I spoke with the Prime Minister this morning by phone and the European Commission and I do think we are making progress but there are issues that need to be resolved and hopefully that can be done today, allowing us to ratify it at the European Council tomorrow, and allowing the House of Commons to give its view on it on Saturday, but if it's not there is still more time.

"The October 31 is still a few weeks away and there is a possibility of another summit before that if we need one.

"A lot of things have changed in the last three years, many twists and turns, but what's never changed is our objectives.

"Our objectives are simple ones, avoiding a hard border between north and south, ensuring the all-island economy will continue to thrive and prosper, for north-south cooperation to resume, as envisaged in the Good Friday Agreement, and protect the integrity of the single market.

"Although time is running short, I am confident these objectives can be achieved.

"In the meantime, we must continue to make our plans and prepare for No Deal, because we have to prepare for the worst case scenario no matter what."

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Varadkar will travel to Brussels for the EU summit tomorrow, where negotiators are currently in the "tunnel" stage of negotiations.

At the same event, Irish agriculture minister Michael Creed said there is some room for optimism.

"This time last week we were probably engulfed in darkness and depression in the context of Brexit," he said.

"There is some room for optimism now but we're not there yet. However, I would countenance if we do get a deal in Brussels on Brexit we have been here before with the Withdrawal Agreement which didn't get through the House of Commons so there are some hurdles to be cleared yet and I'm not underestimating those in any way.

"They are significant and reflective of the magnitude of the challenge, but we remain hopeful."