Fears the EU is trying to trap Northern Ireland into a permanent border backstop can be put to bed, the Taoiseach said.
Leo Varadkar urged British MPs to agree the “positive” proposals and lift the “dark cloud” surrounding the EU withdrawal process.
Two documents endorsed jointly between the EU and the Prime Minister in Strasbourg did not reopen the withdrawal agreement, he said.
They gave instead an additional layer of “interpretation, clarification and elaboration” to the UK on a “legal footing” ahead of this evening’s Westminster vote.
Mr Varadkar said: “The further texts agreed yesterday provide the additional clarity, reassurance and guarantees sought by some to eliminate doubts or fears, however unreal, that the goal of some was to trap the UK indefinitely in the backstop.
“It is not – these doubts and fears can be put to bed.”
On Monday, Cabinet ministers in Dublin held emergency meetings to be briefed about developments between the Prime Minister and the Commission in Strasbourg.
The Taoiseach spoke with EU negotiator Jean-Claude Juncker on the phone.
During a Dublin press conference on Tuesday morning Mr Varadkar said: “In the context of tonight’s vote in Westminster, the outcome from yesterday’s meeting with Prime Minister May and President Juncker is positive.
“I hope and trust that the withdrawal agreement will now be endorsed by the House of Commons.”
He was due to fly to the US on Monday evening for his annual St Patrick’s celebration trip, but his plans were changed at the last minute to accommodate Monday’s unscheduled cabinet meeting.
The Democratic Unionists’ 10 MPs prop up Theresa May’s minority Government and they have repeatedly called for legal guarantees around any deal before they can support it.
The Taoiseach said: “The instrument agreed yesterday puts those assurances on a legal footing and represents an unambiguous statement by both parties of what has been agreed.
“It does not reopen the withdrawal agreement, or undermine the backstop or its application.
“It says that we will work together, in good faith, in pursuit of a future relationship that ensures that the objectives of the protocol (backstop), particularly the need to avoid a hard border, are met.”
He said the Irish Government was committed to exploring alternatives to the insurance policy in a timely way, in the event that the overall future relationship cannot be concluded in a satisfactory and timely manner.
Mr Varadkar warned: “But it does not call into question that the backstop will apply unless and until better arrangements are agreed, with all parties using good faith and best endeavours to that aim.”
He said the newly-agreed texts recalled the dispute resolution mechanisms in the Withdrawal Agreement that could be invoked were either party to demonstrate bad faith, including the possibility of seeking a ruling from a panel of arbitrators.
“I hope that, together with the joint statement on the political declaration, it will provide a basis on which we can move forward again.”
Mr Varadkar said the threat of the UK leaving the EU with no deal had been a dark cloud for many months.
“A positive vote tonight can remove that cloud and restore confidence and optimism in Britain, Ireland and across the EU.”