LONDON — Microsoft violated European Union antitrust rules with ''possibly abusive'' practices by tying its Teams messaging and videoconferencing app to its widely used business software, the bloc said.

The European Commission said Monday it informed Microsoft of its preliminary view that the U.S. tech giant has been ''restricting competition'' by bundling Teams with core office productivity applications such as Office 365 and Microsoft 365.

The commission, the 27-nation bloc's top antitrust enforcer, said it suspects Microsoft might have granted Teams a ''distribution advantage'' by not giving customers a choice on whether to have Teams when they purchased the software. The advantage might have been widened by limits on the ability of rival messaging apps to work with Microsoft software, it said.

''We are concerned that Microsoft may be giving its own communication product Teams an undue advantage over competitors, by tying it to its popular productivity suites for businesses,'' Margrethe Vestager, the commission's executive vice-president for competition policy, said in a statement.

''And preserving competition for remote communication and collaboration tools is essential as it also fosters innovation on these markets.''

The commission took aim at Microsoft a day after accusing Apple of breaching the bloc's new digital competition rulebook, in a flurry of regulatory action underlining Brussels' leading role as a watchdog for Big Tech companies.

Microsoft made some changes last year in an effort to head off an penalty, including offering the software packages without Teams for European customers. But the commission said Tuesday the changes are not enough to address its concerns and that it needs to do more to "restore competition."

''Having unbundled Teams and taken initial interoperability steps, we appreciate the additional clarity provided today and will work to find solutions to address the Commission's remaining concerns.'' Microsoft President Brad Smith said in a prepared statement.

In April, the company also gave customers worldwide the option to get Microsoft 365 and Office 365 without Teams. The two software suites include programs like Word, Excel and Outlook.

Microsoft now has a chance to respond to the accusations, formally known as a statement of objections, before the commission makes its final decision. The company could face a fine worth up to 10% of its annual global revenue, or be forced to carry out ''remedies" to satisfy the competition concerns.

The commission opened its investigation in July 2023 after rival Slack Technologies, which makes popular workplace messaging software, filed a complaint with Brussels. Alfaview, which makes videoconferencing software, also filed a separate complaint.

Slack, owned by business software maker Salesforce, had alleged that Microsoft abused its market dominance to eliminate competition — in violation of EU laws.

''The Statement of Objections issued today by the European Commission is a win for customer choice and an affirmation that Microsoft's practices with Teams have harmed competition,'' Salesforce President Sabastian Niles said. ''We appreciate the Commission's thorough investigation of Slack's complaint and urge the Commission to move towards a swift, binding, and effective remedy that restores free and fair choice and promotes competition, interoperability, and innovation in the digital ecosystem.''