"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. Post-Brexit tensionsEU 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.