Leo Varadkar said there is still “a very wide gap” between the UK and the EU on Brexit.
He was speaking after meeting with Boris Johnson on Tuesday night – just hours after the PM was also rebuked by the Supreme Court for proroguing parliament.
The Taoiseach said of the meeting: “We got to talk about some of the detail of the Withdrawal Agreement and the backstop.
“I think it was a good meeting in the sense that we were able to get into more detail this time.
“However, there is still a very wide gap between the EU and the UK in terms of achieving what we need to achieve before October.”
Mr Johnson’s meeting with the Taoiseach came just hours after the shocking news for Mr Johnson that Parliament is to be reopened today.
An extraordinary decision in the UK Supreme Court saw Mr Johnson’s decision to prorogue parliament overturned.
After the meeting with the Taoiseach, the Prime Minister said he was “cautiously optimistic” about reaching a deal.
He added: “We’ve been talking about the progress we’re wishing to make, our discussions on Brexit, that probably the best thing there would be if we got on and did it in the short time that we have.
“I suppose it would be that we remain cautiously optimistic, but still cautious.”
Mr Varadkar said he did not want to get involved in internal UK politics, but he did say he was not joining in the snap calls for Mr Johnson to resign.
He added: “You know, whoever is the prime minister of the United Kingdom is somebody we’re going to work with.
“And it’s not up to us to decide who the prime minister of the UK is.
“That’s an appointment made by the Queen based on the composition of the House of Commons.”
He added: “I think the negotiations have always been complicated by the fact the UK Parliament is very divided.
“We saw Prime Minister May attempting to get a deal and different versions of a deal through on three occasions.
“And I think any deal that might be made would also face some grave difficulties going through the House of Commons.”
