"This is not about EU v UK. This is a problem with AstraZeneca," claimed an EU diplomat this morning.
He and I were discussing the latest thorny chapter in EU efforts to secure the Oxford-AstraZeneca jabs written into the bloc's contract with the Anglo-Swedish pharmaceutical company.
The debate is now focused on a production plant in the Netherlands, manufacturing AstraZeneca vaccines.
Boris Johnson is calling a number of EU leaders ahead of their meeting on Thursday, to try to ensure that AstraZeneca jabs - or components of jabs - produced in the Halix factory won't be blocked by the EU and kept from the UK.
EU officials say there has been no formal request by the UK for an export from Halix - yet.
But the already-existing cross-Channel strains surrounding the vaccine are infamous by now.
The EU insists AstraZeneca made different and contradictory promises to Brussels and to the UK in their respective contracts, signed last year.
They say the EU-AstraZeneca contract promised:
to ensure vaccine deliveries to the EU using production facilities in both the EU and UK
an assurance from AstraZeneca that it had no other contracts which could get in the way of it fulfilling its commitments to the EU
"Yet at the same time, AstraZeneca appears to have promised the UK priority for the first X million doses - using production facilities in the EU, as well as the UK. This doesn't add up. Though this isn't the UK's fault," concluded the first EU diplomat I spoke to this morning.
"If you include the 20 million AZ doses promised to us already in December, that's 120 million jabs we expected from AstraZeneca by the end of this month. If the EU sees 30 million of those, we'll count ourselves lucky," the diplomat snorted.
AstraZeneca denies that it is failing to honour its contract with the EU. It says the contract commits the company to making the "best reasonable efforts" - which, it says, it is doing, faced with production challenges.
EU frustration with AstraZeneca has been boiling for months now.
And - whatever protestations you hear in Brussels to the contrary - there has been political spillage into EU attitudes towards the UK.
Don't forget: when the AZ delivery row with Brussels first exploded in January, the EU was still smarting from Brexit, bruising trade negotiations with the UK and ongoing bilateral frustrations around implementing the Brexit deal on Northern Ireland.
That seems to have given an extra dimension to the ire of many an EU politician, when AstraZeneca continued (until very recently) to apparently seamlessly deliver jabs to the UK, even while it defaulted significantly on pledges made to the EU.
UK officials point to jabs and digs they say have been made by EU figures. Attempts, they say, to undermine Britain's comparatively speedy and successful vaccine rollout.
EU leaders, like France's President Emmanuel Macron, are accused by some in the UK of seeking to undermine the Oxford-AstraZeneca jab because of its links with Britain.
Back in January Mr Macron described the AZ jab as "quasi-ineffective" in the over-65s. He then changed his mind, as the French government later approved the vaccine for the older population.
Others in the UK say they didn't appreciate it when the EU appeared to question the safety of the UK medical regulatory body granting emergency approval to the Oxford-AstraZeneca vaccine, while the EU chose a slightly longer approval process.
But EU politicians point the finger at the UK too. They accuse UK politicians and media of trying to score political points against Brussels, post-Brexit, using the vaccine rollout.
"The UK never dwells on the fact that the US has yet to approve the AstraZeneca jab," an EU official complained to me. "The criticisms are just about us (the EU)."
"There's so much post-Brexit triumphalism in the UK," complained a representative of another EU country.
"They often claim their vaccine programme would never have been such a success if it hadn't been for Brexit. But that's not true. Even if the UK had stayed a member state, it could have gone its own way over vaccines."
UK diplomats point to what they describe as the "more measured tones" of Prime Minister Johnson as regards vaccines and the EU. They insist that this is key as, they say, vaccine plans come from the "highest levels" of government.
As for the Halix plant in the Netherlands, the EU and Downing Street appear to be seeking some kind of compromise.
I'm told that talks are ongoing. A sign, say UK diplomats, that both sides are engaged in finding a solution.
The diplomats insist it's not in anyone's interest to have vaccines or vaccine components "sitting in a warehouse" when the aim - on both sides of the Channel - is to get needles into arms.
EU export ban?
The Halix plant in the Netherlands hasn't yet received an EU licence to deliver vaccines or components of vaccines to member states, although the European Commission says the green light is expected soon.
It's not clear what happened with the delivery of 250,000 AstraZeneca vaccines destined for Australia that Italy impounded a few weeks ago, with European Commission approval.
Current EU rules allow member states to bloc vaccine exports leaving the EU, if the company producing the doses has failed to fulfil its contract with the EU.
Officials in Brussels say right now that only applies to AstraZeneca.
Now the European Commission wants to get even tougher - possibly blocking exports of any vaccine produced in the EU, destined for a country outside that has its own vaccine production capabilities and a vaccine rollout considerably ahead of the EU.
Without mentioning the UK specifically, this would certainly apply to the UK.
EU leaders aren't united in favour of this latest Commission proposal, as is likely to become apparent during their summit on Thursday. Most say they would prefer a negotiated solution.
On Monday, Ireland's Prime Minister (Taoiseach) Micheál Martin said any EU restrictions on vaccine exports would be a "retrograde step" that could undermine the supply of raw materials for vaccine production.
Chief European Commission spokesman Eric Mamer said Brussels was not seeking to block exports, it was aiming to secure the vaccine supply it was promised. He said the EU was currently considering which tools to use to achieve that.
The Commission, meanwhile, has been blamed