The European Commission says the Swedish-British laboratory has failed in its obligations.
In the first quarter of the year, the group delivered 30 million doses out of the 120 million it was contractually obliged to supply.
For the second quarter, it plans to deliver 70 million of the 180 million it had initially promised.
As the contract is governed by Belgian law, an emergency hearing will take place on 26 May before a Brussels court.
It is understood AstraZeneca is delivering doses at a rate of 10 million per month - well below the planned schedule.
"In the summary proceedings, we ask for the delivery of these 90 million doses that should have been delivered in the first quarter," said a spokesman for the commission.
"We ask that the court asks the company to make the deliveries. In the event that it does not respect this obligation, we can ask for the payment of penalty payments," he added.
AstraZeneca has said it will contest an initial law suit. It said would also fight the latest legal threat.
Last week, Thierry Breton, the European commissioner for internal trade, said the bloc was not going to order any more doses of the vaccine from the company.
