Taoiseach Leo Varadkar has said the instrument agreed yesterday between the UK and the European Union on Brexit does not change the Withdrawal Agreement or undermine the backstop.
Speaking at Government Buildings, Mr Varadkar said: "It does not reopen the Withdrawal Agreement or undermine the backstop or its application.
"It says we will work together in good faith in pursuit of a future relationship that ensures the objectives of the protocol, particularly the need to avoid a hard border, are met."
The Taoiseach said the deal agreed last night was "complementary" to the Withdrawal Treaty, which could not be rewritten.
Mr Varadkar added: "The further agreement yesterday provided additional clarity, reassurance and guarantees sought by some to eliminate doubt or fears, however unreal, that the goal was to trap the UK indefinitely in the backstop.
"I hope and trust the Withdrawal Agreement will now be passed by the House of Commons."
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British MPs were told the joint instrument agreed by Prime Minister Theresa May and European Commission President Jean-Claude Juncker "reduces the risk" that the UK would be trapped in the backstop.
"These doubts and fears can now be put to bed," Mr Varadkar said.
He added that while the instrument committed the EU to exploring alternatives to the backstop should a future relationship between the two not be concluded in a satisfactory and timely manner, it did not call into question that the backstop will apply unless and until such arrangements are agreed.
"In many ways Brexit has been a dark cloud ... A positive vote tonight can remove that cloud and restore confidence and optimism in Britain, Ireland and across the European Union," Mr Varadkar said.
However, UK Attorney General Geoffrey Cox has said that while the agreements "reduce the risk" that the UK could be trapped indefinitely in the backstop, they do not remove it altogether.
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The Government held a late night Cabinet meeting and the hope is now that the agreement would get a majority backing in Westminster.
As ministers were updated on the final text of the assurances offered to the UK, there was one clear message, which was that nothing has been agreed that undermines the backstop.
It is understood that ministers were reassured on this point by Mr Varadkar, Tánaiste and Minister for Foreign Affairs Simon Coveney and Attorney General Seamus Woulfe.
The meeting adjourned for a period when the Taoiseach spoke by phone to Mr Juncker.
Just before midnight the meeting ended on a note of cautious optimism.
The Tánaiste briefed opposition Brexit spokespeople by phone at around midnight shortly after the Cabinet broke up.
In Strasbourg, Mr Juncker said: "I have spoken to the Taoiseach this evening who would be prepared to accept this solution in the interest of securing an overall deal."
The series of documents, which are separate to the agreed withdrawal deal, are designed to provide added assurances to the UK that it will not be tied to the Irish border backstop indefinitely.
Mr Varadkar was due to fly to the United States last night for his annual St Patrick's trip, but his plans were changed at the last minute to accommodate the unscheduled Cabinet meeting.
Earlier yesterday, Mr Varadkar had said any extension to the UK leaving the EU must have a purpose.
Additional reporting Michéal Lehane, Reuters, PA