The European Commission has insisted AstraZeneca has a 'moral obligation' to fulfill its contract for COVID-19 vaccines.
The company's CEO has claimed it never agreed to a specific timeline, and would deliver doses on a "best effort" basis.
However, the European Commission says that explanation is "neither correct nor is it acceptable".
Recent days have seen an escalating row between the two sides, after AstraZeneca announced that production issues mean the EU will be receiving a substantially lower supply of the vaccine in the coming months than initially expected.
The reduction in supply means Ireland is expected to get around 300,000 doses, instead of an expected 600,000, by the end of March.
In a lengthy interview with Italian newspaper la Repubblica, AstraZeneca CEO Pascal Soriot said the contract stated his firm would "make our best effort" to supply the vaccines.
He said "emotions are raw" in Europe and elsewhere over the situation.
In the wake of those comments, EU Commissioner Stella Kyriakides today said vaccine companies have "moral, societal and contractual responsibilities, which they need to uphold".
She said: "The view that the company is not obliged to deliver because we signed a ‘best effort' agreement is neither correct nor is it acceptable.
"Not being able to ensure manufacturing capacity is against the letter and the spirit of our agreement.
"We remain always open to engage with the company to resolve any outstanding issues in the spirit of true collaboration and responsibility.
"That was always the spirit of our engagement with vaccine manufacturers since last spring."
She added that she's calling on AstraZeneca to "engage fully, to rebuild trust, to provide complete information and to live up to its contractual, societal and moral obligations".
The two sides are due to meet again tonight, after earlier reports that AstraZeneca had pulled out of the scheduled meeting - reports the company has since denied.
