EU officials confessed on Saturday to a "blunder" in invoking Northern Ireland Brexit emergency powers during a showdown with Britain over vaccines, and London said it expected its supply of COVID-19 shots would not be interrupted.

The European Union has fallen far behind Britain and the United States in the race to vaccinate its public. It announced on Friday it would impose export controls on vaccines, widely seen as a threat to prevent doses from being sent to Britain.

But it was forced to reverse part of the announcement within hours, after both Britain and Ireland complained about plans to impose emergency export controls for vaccines across the land border between Ireland and British-ruled Northern Ireland.

"They have recognized they have made a mistake and I believe we can now concentrate on making sure that our vaccine program is successful," Michael Gove, a senior British cabinet minister, told Sky News.

Britain's Foreign Secretary Dominic Raab tweeted: "I was reassured the EU has no desire to block suppliers fulfilling contracts for vaccine distribution to the UK."

"The world is watching and it is only through international collaboration that we will beat this pandemic."

EU officials acknowledged that the decision to invoke emergency powers to control trade across the Northern Irish border had been a mistake. Preventing controls at the border was the central issue in five years of Brexit negotiations.

"It's a lot better to realize early on that something might be a problem and to change it, than to stick to your guns and dig a hole for yourself," an EU official said on Saturday.

"As soon as it became apparent that there would be a political difficulty and sensitivity there, in particular on the Irish and Northern Irish side, we decided to take it out.”

Another EU official called the drama "simply and plainly a blunder."

Politicians in the EU are under intense pressure to explain why their countries have managed just a fraction of the vaccinations achieved in Britain, which left the single market four weeks ago.

EU officials were furious earlier this month when British-Swedish drugmaker AstraZeneca announced that most of the vaccine doses it had promised to deliver to the EU by March would be delayed because of production problems in Belgium.

AstraZeneca has been making millions of doses in Britain, but it told the EU it could not divert any to the continent until it fulfills a contract with London. Meanwhile, Britain has been importing EU-made doses of a separate vaccine from Pfizer and BioNTech.

The EU announced regulations on Friday to control exports of vaccines, widely seen as an implicit threat to block Pfizer shipments to Britain unless London shared its AstraZeneca shots.

But imposing restrictions on the Northern Irish border was a bridge too far, after five years of Brexit negotiations to keep it open. The issue is central to a 1998 peace deal that ended 30 years of conflict in Northern Ireland.

Ireland's European Affairs Minister Thomas Byrne said Dublin had not been consulted on the move.

"This type of provision is standard in trade agreements but in the Northern Ireland situation, it obviously has a different political resonance and it's perhaps the case that this wasn't fully appreciated by the drafters,” he told Newstalk radio. "Clearly a mistake was made."