(Bloomberg) -- Amazon.com Inc. must pledge to fairly rank rival robot vacuum cleaners sold on its online marketplace if it is to secure European Union approval for its $1.4 billion buyout of Roomba maker iRobot Corp., the bloc’s interim competition chief Didier Reynders warned. 

His comments follow last week’s move by the European Commission to issue a formal statement of objections cataloging potential reasons to block the deal unless Amazon comes up with an offer to fix them. 

“The main issue is to be sure to have a fair treatment of all the different actors,” Didier Reynders, the EU’s acting commissioner for competition, told reporters after an event in Brussels. 

Reynders, who’s standing in for competition commissioner Margrethe Vestager while she runs for the top job at the European Investment Bank, said that Amazon should commit to ensuring the visibility of correct and transparent information on rival vacuums, and rank them fairly on the company’s marketplace platform. 

In last week’s filing, the EU’s antitrust arm said Amazon could be tempted to demote other robot vacuum cleaners on its platform and promote its own products with such labels as “Amazon’s choice” or “Works With Alexa.” The commission also said Amazon may find it “economically profitable” to shut out rivals.

While getting a statement of objections signals the EU has serious concerns with a transaction, most merging companies avoid a veto by addressing competition issues. Companies also have the right to challenge the preliminary findings of regulators in writing or at a hearing.

The robot-vacuum maker’s stock was trading at around $37.28 at 11:00 a.m. in New York, about 28% below Amazon’s $51.75-per-share offer

Amazon didn’t immediately respond to a request for comment. 

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