BRUSSELS, May 10 (Reuters) - AstraZeneca Plc has delivered 50 million doses of its COVID-19 vaccine to European Union countries, according to EU supply data, a milestone the company had originally been expected to hit in January.

The volumes delivered make up just one-sixth of total commitments so far, and the European Commission is set to launch on Tuesday a second legal case against AstraZeneca over delayed deliveries, a spokesman for the EU executive said on Monday.

Repeated cuts to supplies, which contributed to delays in the EU's vaccination drive, pushed the EU Commission to sue the Anglo-Swedish drugmaker in late April in a bid to get more doses by mid-year.

On Tuesday, it will launch a new case on the merits of the issue, which an official familiar with the proceedings said was mostly procedural but would allow the EU to seek potential financial penalties.

AstraZeneca had shipped nearly 50 million doses as of May 7, an EU official told Reuters on Monday, citing the latest EU internal figures on vaccine supplies.

In mid-March, the company had pledged to deliver 50.2 million doses to the EU by the end of April, an AstraZeneca document seen by Reuters showed.

But AstraZeneca had shipped only 47.6 million doses by April 30, a spokesman for the company said, adding that other doses were sent over the first weekend of May and in the following days, "following requests to not ship to a few countries that had public holidays during this period".

Immediately after the EU sued the company, AstraZeneca issued a statement on April 26 saying it would deliver "almost 50 million doses to European countries by the end of April".

Under its contract with the EU, the company had committed to its "best reasonable efforts" to deliver 300 million doses by the end of June, of which 70 million were supposed to be delivered by the end of January.

Citing production problems and export restrictions, AstraZeneca in March said it would deliver to the EU only 100 million doses by the end of June. It delivered 30 million in total by the end of March.

The vaccine was approved for use in the EU in late January, but the EU Commission has said AstraZeneca should have applied earlier.

The EU wants to receive as many doses as possible of the 300 million contracted, but in a further sign of its lost confidence in AstraZeneca, it has already decided not to take up an option within the contract for 100 million additional doses.

On Sunday, EU industry commissioner Thierry Breton said the commission was also not planning to negotiate a new contract with the firm.

(Reporting by Francesco Guarascio; Editing by Bill Berkrot and Bernadette Baum)