Austria, Bulgaria, Croatia, the Czech Republic, Latvia and Slovenia raised concerns over COVID-19 vaccine distribution in a call with the head of the European Council on Wednesday, Reuters news agency quoted a European Union official as saying.

European Council President Charles Michel, who chairs EU summits, discussed the matter with leaders from the six countries on Wednesday. The bloc's 27 EU ambassadors will address this later in the day, the official said.

“Leaders shared their concerns with (Michel) on possible gaps in the vaccine distribution between member states following the fact that one company has not respected its commitment,” the official said, under the condition of anonymity.

Austrian Chancellor Sebastian Kurz said on Tuesday he and allies from eastern Europe were pushing for the EU to adjust the way it distributes COVID-19 vaccines. The EU faces an acute squeeze of COVID-19 jabs due to reduced deliveries by AstraZeneca, Reuters said.

The six leaders wrote to Michel and European Commission chief Ursula von der Leyen last week, warning that the vaccine distribution process did not reflect the size of the population of each member state as previously agreed.

The Commission has said in the meantime that member states decided to depart from its proposal for the allocation of vaccine doses on the basis of a pro rata of the population of each member state.

“Under this system, if a Member State decides not to take up its pro rata allocation, the doses are redistributed among the other interested Member States. Member States have used this system to modify the pro rata allocation proposed by the Commission under all 6 Advance Purchase Agreements. It would be up to the Member States to find an agreement if they wished to return to the pro rata basis,” the Commission said on Saturday.