Amazon.com Inc.’s $1.65 billion plan to buy vacuum cleaner maker iRobot Corp. is headed for an in-depth European Union probe unless the ecommerce firm makes an immediate offer that allays antitrust concerns.

The likely move from EU antitrust regulators will be announced before a deadline of July 6, said a person familiar with the matter who asked not to be named because the process isn’t public. The step was first reported by Reuters.

The decision would put the European Commission at odds once again with Britain’s Competition and Markets Authority, which last week gave the deal the green light after concluding that iRobot has a modest market power.

The two regulators have previously reached divergent decisions on Microsoft Corp.’s $69 billion takeover bid for games developer Activision Blizzard Inc. — with the EU giving the deal the nod, while the CMA wielded a veto.

So-called phase 2 probes add about 90 working days to deal reviews. Regulators typically demand remedies to solve competition concerns but sometimes also decide to give their unconditional approval if initial concerns are shown to be unfounded.

Foxglove, a London-based tech advocacy group, earlier this year urged the EU to investigate and block the planned transaction, expressing “grave concerns” the deal will “cause harm to consumers and competition in ways that cannot necessarily be fully conceived of today.”

The European Commission and Amazon declined to comment.