PARIS — The president of the European Council vowed Sunday to make drug companies fulfill their vaccine contracts with EU countries, but acknowledged it will be hard for the bloc to meet its goal of vaccinating 70% of the adult population by late summer.

Amid criticism in EU countries of disruption of vaccine deliveries from Pfizer, Charles Michel said on France’s Europe-1 radio: “We plan to make the pharmaceutical industry respect signed contracts.” He said EU officials “pounded our fist on the table” with Pfizer last week to ensure the delays end by this coming week.

However, given logistical challenges and the slow rollout of vaccines in the EU so far, he said “it will be difficult” to meet the aim of the EU’s executive Commission of vaccinating 70% of the adult population by the end of the summer.

The EU has sealed six vaccine contracts for more than 2 billion doses, but only the Pfizer-BioNTech and Moderna vaccines have been approved for use so far. The European Medicines Agency is scheduled to review the Oxford-AstraZeneca vaccine on Friday.