The EU threatened to ban exports of vaccines to the UK on Wednesday (March 17).
The bloc said this is to safeguard doses for its own citizens facing a third wave of the health crisis.
European Commission head Ursula von der Leyen:
"All options are on the table. We are in the crisis of the century and I'm not ruling out anything for now because we have to make sure that Europeans are vaccinated as soon as possible."
Von der Leyen said the flow of vaccine products was smooth with the U.S.
But she was frustrated over a lack of deliveries from AstraZeneca in Britain.
"If this situation does not change, we will have to reflect on how to make exports to vaccine-producing countries dependent on their level of openness. So we are exporting a lot to countries that are themselves producing vaccines and we think this is an invitation to be open."
Six EU countries complained to Brussels about deliveries of vaccines, while France, Germany and others have suspended AstraZeneca jabs for safety checks.
The situation threatens Commission plans to launch a 'green digital certificate' which would gather information on vaccinations, tests and recovery.
It is hoped the pass could help travellers to cross borders freely again.