German Chancellor Angela Merkel on Tuesday voiced support for EU chief Ursula von der Leyen's threat to block AstraZeneca vaccines produced in the bloc from being exported, ahead of a crunch EU summit on the escalating row.

"I support Commission President Ursula von der Leyen," said Merkel.

"We have a problem with AstraZeneca," she added.

European officials are furious that AstraZeneca has been able to deliver its UK contract in full while falling short on its supplies to the EU.

In her tough warning to the Anglo-Swedish pharmaceutical giant last Saturday, von der Leyen said: "That's the message to AstraZeneca: you fulfil your contract with Europe first before you start delivering to other countries."

European officials are furious that AstraZeneca has been able to deliver its UK contract in full while falling short on its supplies to the EU
European officials are furious that AstraZeneca has been able to deliver its UK contract in full while falling short on its supplies to the EU AFP / JUSTIN TALLIS

The warning comes as the European Union struggles to speed up its Covid-19 inoculation campaign, just as many member states are facing a third coronavirus wave and renewed curbs on public life.

Von der Leyen said AstraZeneca had delivered only 30 percent of the 90 million vaccine doses it had promised for the first quarter of the year.

Much of the frustration is over supplies to Britain, where the inoculation campaign has progressed at a much faster pace and where AstraZeneca also has production facilities.

Brussels has accused London of operating a de facto export ban to achieve its vaccine success, a claim furiously denied by Prime Minister Boris Johnson's government.

Britain has in turn voiced alarm over the EU's threat to halt AstraZeneca supplies leaving the continent.

Merkel said both herself and France's Emmanuel Macron had spoken with Johnson on the issue, and that a summit of EU leaders later this week will address the subject.

Coronavirus