The EU will not trigger the Article 16 safeguard clause of the Northern Ireland Protocol over the exporting of Covid-19 vaccines, a statement from the Commission has confirmed.
The move was welcomed by both Taoiseach Micheál Martin and Minister for Foreign Affairs Simon Coveney.
Mr Martin told RTÉ News he had pointed out the implications of such a move to the European Commission President in discussions throughout the evening.
"Welcome decision by the European Commission tonight not to invoke the safeguard clause of the Ireland / Northern Ireland Protocol following constructive discussions with Ursula von der Leyen," he said on Twitter.
"This is a positive development given the many challenges we face in tackling Covid-19."
Minister Coveney, also posting on Twitter, commented: "Welcome news, but lessons should be learned; the Protocol is not something to be tampered with lightly, it's an essential, hard won compromise, protecting peace & trade for many."
The commission statement said: "To tackle the current lack of transparency of vaccine exports outside the EU, the Commission is putting in place a measure requiring that such exports are subject to an authorisation by Member States.
"In the process of finalisation of this measure, the Commission will ensure that the Ireland/Northern Ireland Protocol is unaffected. The Commission is not triggering the safeguard clause.
"Should transits of vaccines and active substances toward third countries be abused to circumvent the effects of the authorisation system, the EU will consider using all the instruments at its disposal.
"In the process of finalising the document, the Commission will also be fine-tuning the decision-making process under the implementing regulation.
"The final version of the implementing regulation will be published following its adoption tomorrow."
The Irish Government was not given advance warning of the European Commission's plan to trigger Article 16 of the protocol to bring about new monitoring controls on exports of Covid-19 vaccines, RTÉ News understands.
Irish officials were said to "very concerned" and "shocked" at the implications of such a move.
It is understood the Taoiseach's department was contacted late this afternoon, but only after the Commission had announced its intended action.
Senior government sources indicated that the Government's concerns were taken onboard, following a number of direct discussions between the Taoiseach and European Commission president.
In a tweet, Ms von der Leyen confirmed she had spoken to Mr Martin "to agree on a satisfactory way to introduce an export authorisation mechanism for Covid vaccines".
I spoke to Taoiseach @MichealMartinTD this evening to agree on a satisfactory way to introduce an export authorisation mechanism for COVID vaccines.— Ursula von der Leyen (@vonderleyen) January 29, 2021
The proposed new transparency mechanism is designed to ensure that vaccines which are contractually destined for EU member states are not, instead, exported out of the EU.
According to a senior source, European Commission officials feared that the Northern Ireland Protocol could be a loophole.
That is because the protocol ensures there can be no impediment on exports to Northern Ireland from the EU, but also because there is unfettered access for goods moving from Northern Ireland to Britain.
For that reason, it is understood the Commission decided to consider an emergency triggering of Article 16 of the protocol, which allows either side to take safeguard measures in the event of a serious societal or economic threat.
Ms von der Leyen, in a another Twitter post, said she had "constructive talks" with British Prime Minister Boris Johnson tonight.
"We agreed on the principle that there should not be restrictions on the export of vaccines by companies where they are fulfilling contractual responsibilities."
Mr Martin also spoke to the British Prime Ministe about the issue.
A No 10 spokesman said: "The Prime Minister this evening had a constructive discussion with the Taoiseach Micheál Martin.
"The PM set out his concerns about the EU's use of Article 16 of the Northern Ireland Protocol and what these actions may mean for the two communities in Northern Ireland.
"The PM stressed the UK's enduring commitment to the Belfast/Good Friday agreement and said the EU must urgently clarify its intentions and what steps it plans to take to ensure its own commitments with regards to Northern Ireland are fully honoured."
Mr Johnson also expressed his "grave concerns" to Ms von der Leyen over the potential impact on the exports of coronavirus vaccines caused by the bloc's actions, No 10 said.
Downing Street warned the EU that "as a friend and ally" it should not attempt to disrupt UK vaccine supplies.
A spokesman said: "The UK government is urgently seeking an explanation from the European Commission about the statements issued by the EU today and assurances as to its intentions.
"The UK has legally-binding agreements with vaccine suppliers and it would not expect the EU, as a friend and ally, to do anything to disrupt the fulfilment of these contracts.
"The UK government has reiterated the importance of preserving the benefits of the Belfast/Good Friday Agreement and the commitments that have been made to the two communities."
Earlier, DUP Leader and First Minister of Northern Ireland Arlene Foster said any triggering Article 16 would be "an incredible act of hostility".
She said the EU was prepared to use Northern Ireland "when it suits their interests".
"At the first opportunity the EU has placed a hard border between Northern Ireland and the Republic of Ireland over the supply chain of the coronavirus vaccine," she said.
Mrs Foster later posted a video on Twitter in which she said: "This is an incredibly hostile and aggressive act by the European Union. They are trying to stop the supply of a vaccine, designed to save lives, into the United Kingdom."
Stormont's Deputy First Minister, Sinn Féin's Michelle O'Neill, also expressed her "serious concerns" over the matter in a post on Twitter.
"I have just spoken with the Irish Government to raise my very serious concerns in relation to the invoking of Article 16. This is a totally ill-judged move by the EU and should not have been triggered.
"Calm heads need to prevail, this needs sorted urgently," she said.
Sinn Féin leader Mary Lou McDonald said any triggering of Article 16 would be a "grave error".
She said on Twitter: "Our citizens need timely access to lifesaving vaccines not trade disputes. Now is a time for cool heads and solidarity."
SDLP leader Colum Eastwood said invoking Article 16 would be "disproportionate and a grave error in judgement by the European Commission".
Additional reporting: Mary Regan, PA news