BRUSSELS (Reuters) - EU antitrust regulators on Tuesday charged Microsoft ( MSFT ) of illegally bundling its chat and video app Teams with its Office product and say that recent moves by the U.S. tech giant to unbundle the package were insufficient and more needed to be done.

"Microsoft ( MSFT ) has breached EU antitrust rules by tying its communication and collaboration product Teams to its popular productivity applications included in its suites for businesses Office 365 and Microsoft ( MSFT ) 365," the European Commission said in a statement.

"The Commission preliminarily finds that these changes are insufficient to address its concerns and that more changes to Microsoft's ( MSFT ) conduct are necessary to restore competition," it said, referring to Microsoft's ( MSFT ) unbundling of Teams from Office announced in recent months.

The move by the EU competition watchdog was triggered by a 2020 complaint by Salesforce ( CRM )-owned competing workspace messaging app Slack.

Teams was added to Office 365 in 2017 for free and subsequently replaced Skype for Business. Its popularity soared during the pandemic due in part to its video conferencing.

Microsoft ( MSFT ) said it would work to find solutions to address EU regulators' concerns.

(This story has been corrected to say 'insufficient' instead of 'sufficient' in paragraph 1)