STORY: Microsoft is in trouble with the EU over its popular collaboration app Teams, and could face a big fine.

Antitrust regulators charged the U.S. tech giant on Tuesday (June 25) of illegally bundling the product with its Office software, making it hard for rivals to compete.

They said the app was given a distribution advantage - while limitations preventing interactions between Teams competitors and Microsoft's offerings hurt rivals.

They also said recent moves to unbundle the package were insufficient and more needed to be done.

The European Commission warned Microsoft needed to make more changes to restore competition.

The move was triggered by a complaint four years ago by Salesforce-owned messaging app Slack.

Teams was added to Office 365 in 2017 for free, and replaced Skype for Business.

Its popularity soared during the pandemic due in part to its video conferencing.

Microsoft said it would work find solutions.

In April, it separated Teams from Office globally to try to resolve EU antitrust concerns.

If the company was fined, it would be the first such punishment in two decades for Microsoft in Europe.