Pharmaceutical giant AstraZeneca and the European Commission have vowed to resolve a deepening row over the company's agreement to supply COVID-19 vaccines to the EU after the bloc accused AstraZeneca of breaching a "binding commitment".

It comes as after they met for crisis talks on Wednesday which both sides noted were "constructive", but which failed to heal the rift.

After the crunch talks, European Health Commissioner Stella Kyriakides took to Twitter on Wednesday evening to express "regret" that there was "continued lack of clarity on the delivery schedule and request a clear plan from AstraZeneca for the fast delivery of the quantity of vaccines that we reserved".

She added: "We will work with the company to find solutions and deliver vaccines rapidly for EU citizens".

Earlier, Kyriakides said the EU had provided investment in return for a "binding commitment" to produce vaccines prior to regulatory approval.

"Not being able to ensure manufacturing capacity is against the letter and the spirit of our agreement," she told a news conference on Wednesday afternoon.

AstraZeneca denies breaching the terms of its contract with the EU, following the revelation that planned supplies are to be cut by 60 per cent compared to levels it had agreed to aim for. It blames glitches in production.

The dispute highlights the tension over vaccine supplies as Europe struggles to roll out inoculation programmes against the coronavirus.

Separately, French firm Sanofi has pledged to help out with vaccine production by boosting distribution of vaccines made by rival producers Pfizer and BioNTech.

EU 'willing to publish AstraZeneca contract'

The EU is willing to publish its contract with AstraZeneca if the company agrees, said Euronews Brussels correspondent Shona Murray, quoting an EU source.

The source added that the EU expects the company to do the maximum possible to produce vaccine dosages as set out in the agreement. Plants outside the EU should be used to make up the shortfall.

Earlier, an EU official said speaking anonymously that the EU would “insist on them” coming back to the negotiating table to explain the delay in deliveries once the Oxford-AstraZeneca vaccine gets approved for use by the European Medicines Agency.

The Commission has briefed that it is looking for "more explicit" reasons from AstraZeneca to explain the reduced production, and that it wants the problem resolved now.

EU sign-up date allowed 'less time' to resolve problems

On Tuesday night, Astrazeneca's boss hit back at criticism from the European Union over plans that will see a huge shortfall in supplies, saying it had only signed up to make a "best effort" to deliver.

"Our contract is not a contractual commitment. It's a best effort. Basically we said we're going to try our best, but we can't guarantee we're going to succeed. In fact, getting there, we are a little bit delayed,” Chief Executive Pascal Soriot said.

The comments came in an interview given on Tuesday to LENA (Leading European Newspaper Alliance) and published in European newspapers.

Soriot added that the EU had ordered its supplies three months after the UK, allowing less time to resolve production issues.

He said there had been some start-up issues in the UK supply chain as well, but "the UK contract was signed three months before the EU contract. So with the UK, we had three more months to resolve the problems encountered".

The CEO also insisted that his company "certainly does not take vaccines from Europeans to sell them elsewhere at a profit".

The laboratory, partnered with the University of Oxford, has pledged not to make a profit on the sale of vaccines during the pandemic.

While the EU regulatory green light for this vaccine is expected on Friday, the British laboratory announced last week that deliveries would be lower than expected in the first quarter due to a "drop in production" at a European manufacturing site.

These relate to up to 400 million doses of the AstraZeneca / Oxford vaccine, which has the advantage of being cheaper to produce than its rivals, while being easier to store and transport.

Brussels raised its tone on Monday in its stand-off with AstraZeneca, deeming the delays in the delivery of its COVID-19 vaccine "unacceptable". The European Commission is now demanding "transparency" on exports outside the EU of doses produced in the bloc.

The slowdown in production has alarmed EU countries, already on edge after difficulties in the delivery of the Pfizer-BioNTech vaccine. It increases the pressure on the European Commission, which negotiated the pre-order contracts on behalf of the EU27.

Sanofi steps in

French drug maker Sanofi has stepped into help ease the panic over the lack of COVID-19 vaccinations in the EU. Sanofi will fill and pack vaccines made by rival producers Pfizer and BioNtech from July in an effort to help meet the huge demand.

The company will aim to help supply more than 100 million doses this year from its German plant in Frankfurt, CEO Paul Hudson told Le Figaro newspaper.

The French government has been pressing Sanofi to use its facilities to help make vaccines from its rivals, given high demand and problems with supplies of the few vaccines that are already available.

Last month, Sanofi and Britain’s GlaxoSmithKline said a vaccine they are jointly developing had showed an insufficient immune response in older people, delaying its launch to late this year.

European Commission President Ursula von der Leyen repeated on Tuesday a call for vaccine producers to deliver on schedule.

“Europe invested billions to help develop the world's first COVID-19 vaccines," she told the World Economic Forum's virtual event in Switzerland. “And now, the companies must deliver. They must honour their obligations."

The Commission has raised the possibility of strict export controls on doses made in the bloc in its demands for more information about vaccine production.

"Let me just emphasise the word that is important here is: transparency. This is not about blocking. This is about knowing - what the companies are exporting or will export to markets outside of the European Union," said Commission spokesman Eric Mamer.

The slow rollout of vaccine distribution in Europe led Hungary to order doses from Russia, the country's Foreign Minister Péter Szijjártó told Euronews this week.

Meanwhile, the operation in Germany has drawn criticism from the Governor of Bavaria, Markus Soeder.

"I think that the populations of Europe are extremely stressed and tired by this pandemic which has lasted for a year. Governments are under pressure," AstraZeneca CEO Pascal Soriot added in his interview, specifying that Europe "which represents 5 per cent of the world's population, will obtain 17 per cent of our production in February".

Soriot also affirmed in his interview that the laboratory is working "with the University of Oxford on a vaccine that will target" the South African variant of COVID-19, a virus more transmissible than the first version of the new coronavirus.