Italy has used its European Union influence to block a shipment of AstraZeneca's coronavirus vaccine to Australia.

The office of the Italian prime minister confirmed the move Friday, stating that it believes that its decision to halt the shipment during the previous day will be backed by the European Commission. The shipment was for 250,700 doses of AstraZeneca's vaccine.

The move is a dramatic escalation of the dispute between the trading bloc and the British-Swedish pharmaceutical company over its vaccine supply. The acrimonious fight between the two began in late January after AstraZeneca announced that it would not be able to meet its previously promised amount of vaccines to EU-member countries.

The European Commission responded by giving member states the power to stop AstraZeneca from exporting its vaccines outside the bloc in certain situations. The move was meant to ensure that AstraZeneca was able to meet its obligations to the bloc ahead of its other customers. The commission said that the rule should not affect COVAX, the global initiative to supply vaccines to poorer countries.

The vaccine programs of EU-member states have mostly faltered as they encountered supply and logistical problems. Some countries have chosen to rely on outside sources to offset AstraZeneca's shortfall. According to data from the World Health Organization, the EU has only been able to administer first doses to about 5.5% of its more than 447 million population.

Italy's Foreign Ministry said that blocking the shipment was justified given AstraZeneca's continued vaccine delivery delays. The ministry said that Australia was not considered a "vulnerable" country by the trading bloc.

The ministry said that AstraZeneca was permitted to export "modest quantities" of its vaccines for scientific research and other purposes. However, the latest shipment was flagged due to the high number of vaccine doses involved.

Under the newly imposed EU procedures, companies within member countries must notify authorities if they intend to export vaccines outside the bloc. Certain criteria must be met before the member state approves the export. After it is approved, the European Commission will have one working day to approve or reject the member state's decision.

Sources with knowledge in the matter said that the European Commission will likely not oppose Italy's decision to block the shipment. AstraZeneca has yet to release a statement in response to the export ban.