Ratings and consumer research firm Nielsen announced an agreement with the Federal Trade Commission that gives it clearance for the proposed $1.3 billion acquisition of Arbitron, which measures radio listening.

But under the terms of the FTC’s approval, Nielsen must continue to support Project Blueprint, the cross-platform project measuring TV, radio, PC, mobile and tablet engagement that ESPN has been working on with Arbitron and comScore.

Nielsen said that subject to customary closing conditions, the Arbitron deal is expected to close on Sept. 30, 2013.

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“We are pleased to have the regulatory process behind us and are excited to be closing the Arbitron acquisition,” Nielsen CEO David Calhoun said in a statement. “We are looking forward to providing all of the benefits of the combined company to our new clients in the radio industry and their advertisers, driving incremental value for them as well as our shareholders.”

Under the agreement, Nielsen must make available to any “FTC-approved third-party” companies that request it a license Arbitron Portable People Meter and related data as well as software and technology currently being used in the ESPN project for the sole purpose of cross-platform measurement for up to eight years.

“Effective merger enforcement requires that we look carefully at likely competitive effects that may be just around the corner,” FTC chairwoman Edith Ramirez said in a statement. “In this matter, the evidence provided us with a strong reason to believe that absent a remedy, the deal was likely to harm emerging competition in the area of cross-platform audience measurement.”