"We're pragmatic. My priority, as far as the vaccines are concerned, is to ensure that the firms we have contracts with deliver them punctually," Breton told BFMTV television.
Brussels had originally ordered 120 million doses of the Anglo-Swedish group's jab for the 27 member states in the first quarter and 180 million in the second quarter.
But the drug maker "only delivered 30 million, thus creating the problems that everyone has seen," Breton said.
And only another 70 million will be delivered in the second quarter, he continued, but added: "Nothing is decided. Talks are still ongoing".
The EU commissioner insisted that any such decision would "not be for epidemiological or medical reasons".
"When looking at the data, the benefits of the AstraZeneca vaccine outweigh the disease," he said.
French industry minister Agnes Pannier-Runacher had suggested on Friday that the EU might not renew its contract with AstraZeneca in 2022 after Denmark became the first European country to stop using the jab altogether over suspected rare but serious side effects.
While other countries also suspended its use, at least temporarily, most have subsequently resumed after the European Medicines Agency (EMA), emphasised the benefits of the vaccine, judging it "safe and effective".
Pannier-Runacher said that the EU had "not started discussions with Johnson & Johnson and with AstraZeneca for a new contract, whereas we have already started discussions with Pfizer-BioNTech and Moderna", the makers of two other vaccines on the market in Europe.
EU Commission chief Ursula von der Leyen also said this week that German biotech firm BioNTech and US pharma giant Pfizer had shown themselves to be "reliable partners, who have honoured their commitments and have reacted quickly with regard to our needs".
In France, 23 cases and eight deaths have been reported of rare blood clots after taking the AstraZeneca jab, out of more than 2.7 million doses administered so far.
Nevertheless, Alain Fischer, an immunologist who heads the government's vaccination advisory board, told French radio on Sunday the benefits of the jab for people aged 55 and over "very much outweighed the risks" of possible complications.
