BRUSSELS (AFP) -- Companies producing Covid-19 vaccines “must deliver”, EU chief Ursula von der Leyen said on Tuesday as tensions mounted between her European Commission and pharmaceutical firms over delayed deliveries.

“Europe invested billions to help develop the world's first Covid-19 vaccines,” she said in a live video address to an online-only version of the annual World Economic Forum usually held in Davos, Switzerland.

“And now, the companies must deliver. They must honour their obligations,” she said.

The Commission is demanding answers of British-Swedish group AstraZeneca and US company Pfizer about delays both have announced to their deliveries to the European Union.

In a sign of concern that pharmaceutical groups might be selling the earmarked doses to higher bidders outside the bloc, it is making a move to require the companies to notify authorities of any exports to outside the European Union.

Von der Leyen underlined that initiative in her speech, saying “we will set up a vaccine export transparency mechanism” to “ensure” the firms meet their contractual obligations to the EU.

The issue is sensitive for von der Leyen, who spearheaded efforts to have the Commission procure more than two billion doses of potential Covid-19 vaccines for the bloc’s 27 member states, home to 450 million people.

Last week -- after Pfizer‘s announced delay but before AstraZeneca’s -- von der Leyen vowed the aim was to inoculate 70 percent of adults in the EU by the end of August. That goal now looks in jeopardy.

The pace of the EU rollout has lagged behind the United States, Britain and Israel, though member states including Malta, Denmark and France have started to accelerate their programmes.

In her speech, von der Leyen said the Commission‘s vaccine procurement was not for the EU alone but also for poorer non-EU countries who are to be supplied through a COVAX vaccination alliance co-led by the World Health Organization.

As part of a longer-term strategy to head off this and future health crises, von der Leyen said the EU would propose a public-private entity under a new European Health Emergency Response Authority.