The move came hours after Commission chief Ursula von der Leyen increased pressure on the company over its decision to reduce supplies to the EU.

The contract signed in August contained "binding orders", she told German radio, and called for an explanation.

The vaccine is expected to be approved by the EU medicines regulator later.

UK-Swedish AstraZeneca is blaming production delays at two plants.

The August deal was for 300 million doses for the European Union to be delivered after regulatory approval, with an option for 100 million more.

But EU sources say they now expect to get only about a quarter of the 100 million vaccines they were expecting to receive by March, a shortfall of about 75 million jabs.

AstraZeneca says the production problems are at its plants in the Netherlands and Belgium.

The EU decided to publish the contract, with the agreement of AstraZeneca, to try to back its argument that the company is reneging on its commitments.

Many parts of the published contract have been redacted - blanked out - to protect sensitive information.

Warning of a 'vaccine war':
"There are binding orders and the contract is crystal clear," Mrs von der Leyen said in Friday morning's radio interview.

"'Best effort' was valid while it was still unclear whether they could develop a vaccine. That time is behind us. The vaccine is there.

"AstraZeneca has also explicitly assured us in this contract that no other obligations would prevent the contract from being fulfilled," she said.

AstraZeneca is producing the jab at its UK plants too and there have been no reported problems with its contract with the UK authorities.