The EU has reversed its decision to temporarily override part of the Brexit deal amid an ongoing row over Covid vaccine supplies in the bloc.
The move could have seen checks at the border of Ireland and Northern Ireland to prevent shipments entering the UK.
But the European Commission later said it would ensure the Northern Ireland Protocol is āunaffectedā.
However, the EU said it had āno choiceā but to press on with introducing export controls on vaccines.
The Brexit deal guarantees an open border between the EU and Northern Ireland, with no controls on exported products.
However, Article 16 of the Northern Ireland Protocol part of the deal allows the EU and UK to choose to suspend any aspects they consider are causing āeconomic, societal or environmental difficultiesā.
Earlier on Friday evening the EU announced it would trigger the clause and introduce the export controls on its vaccines entering Northern Ireland in a bid to prevent the region becoming a backdoor for jabs to be sent to the UK mainland.
It said the actions were ājustifiedā to avert problems caused by a lack of supply.
But the proposals sparked concern from all five parties in Northern Irelandās devolved government and Irish prime minister MicheĆ”l Martin.
The EU insists its controls are a temporary scheme, not an export ban. But the World Health Organization is among those criticising the move, saying it could have a knock-on effect around the world.
But later on Friday evening, following talks with UK Prime Minister Boris Johnson, European Commission President Ursula von der Leyen tweeted that the UK and EU had āagreed on the principle that there should not be restrictions on the export of vaccines by companies where they are fulfilling contractual responsibilitiesā.
She said the backtrack came after āconstructive talksā with Mr Johnson in which he had expressed āgrave concernsā about the initial plan.
The BBCās Brussels correspondent Kevin Connelly said Ms von der Leyenās midnight tweet seemed to āwind downā the idea that there could be a āvaccine warā where jab supplies are prevented from reaching the UK.
āTrumpian actā
Julian Smith, Conservative MP and former Northern Ireland secretary, said the EU had āpulled the emergency cordā without following the proper processes that had been agreed over years of negotiations.
He told BBC Radio 4ās Today programme the move came āwithout anywhere near the level of understanding of the Good Friday Agreement, of the sensitivities of the situation in Northern Irelandā.
āIt was an almost Trumpian act ā Iām very pleased that theyāve changed their minds,ā he said, adding that the EUās āmajor issueā with its Covid vaccine rollout ādoes not excuseā their actions.
āMistake,ā āmisjudgement,ā āblunder.ā
These are just some of words EU insiders have been using privately to describe the European Commissionās initial decision on Friday to suspend areas of the Brexit deal dealing with Northern Ireland, a part of its Covid vaccine row.
Although it then U-turned on those plans, critics say the damage was already done.
Brussels previously lectured the UK government about respecting the Irish Protocol ā which was painfully and carefully drafted during Brexit negotiations.
Now the EU seemed quick to undermine the agreement.
Member state Ireland felt stung that it hadnāt been consulted. This all adds to the impression of chaos surrounding the EUās vaccine rollout.
Brussels was already under fire from a growing number of EU countries for having been slow to sign vaccine contracts with pharmaceutical companies.
This āmishapā over the Irish Protocol as Spainās Foreign Minister called it, hasnāt exactly helped the commissionās reputation.
Mr Martin welcomed the EUās reversal, describing it as a āpositive development given the many challenges we face in tackling Covid-19ā.
However, it was not thought that the move would have directly disadvantaged Northern Ireland, which gets its vaccine supplies through the UK procurement system.
Despite later backtracking on Article 16, the EU is still introducing new controls giving its member states the power to block exports of the coronavirus vaccine to countries including the UK ā should they want to.
The statement from the European Commission said it in order to tackle āthe current lack of transparencyā over vaccine exports outside the EU, it would be introducing a measure requiring that all such exports āare subject to an authorisationā by member states.
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It was the latest development in a deepening dispute over the vaccine producer AstraZenecaās delivery commitments to the EU.
The bloc agreed to buy up to 400m doses of the vaccine AstraZeneca developed last year with Oxford University, and on Friday the EUās drugs regulator approved the vaccineās use for all adults.
But the firm said that due to problems at one of its EU factories, supplies would be reduced by about 60% in the first quarter of 2021. https://emp.bbc.com/emp/SMPj/2.39.13/iframe.html media captionArlene Foster: EU Covid vaccine controls are an āact of aggressionā
While the commission rowed back from the Article 16 threat, the EU warned that it would āconsider using all the instruments at its disposalā should vaccine supplies ātoward third countries be abused to circumvent the effects of the authorisation systemā.
The EUās original move was criticised by a string of politicians, with Northern Irelandās First Minister Arlene Foster describing it as āan absolutely incredible act of hostilityā that places a āhard borderā between Northern Ireland and the Republic of Ireland.
She told the Today programme the debacle highlighted the EUās āvaccine embarrassment and mismanagementā.