Financial details are still being hammered out, but it is understood that under the terms of the deal, Unity would become part of the wider JWT Group and offer independent communications advice.
The new joint venture company is likely to retain the Unity name and would work with Unity clients such as Carphone Warehouse and Kraft, along with JWT clients such as Ford, Nestlé and Kellogg, where appropriate.
However, it would also be free to pitch for additional third-party business.
The agreement is likely to be similar to JWT's relationship with other group companies, which includes the relationship marketing specialist RMG and the direct agency Black Cat.
However, regardless of the eventual ownership structure, Unity's positioning will remain as it is now, with the company offering clients media-neutral communications advice which may, or may not, include traditional advertising solutions.
Unity was founded six years ago by the former BMP DDB media players Derek Morris, Andy Tilley and Ivan Pollard. It was one of the original "fourth-wave" media specialists, which filled the gap left by the separation of the media and creative disciplines.
The deal would put JWT, under its chief executive, Simon Bolton, in the vanguard of major agencies seeking to reintegrate media thinking with their creative product. The partnership would be the latest in a series of creative and media specialist alliances. Last year, Clemmow Hornby Inge joined forces with Naked to offer media advice with a venture called Naked Inside.
Meanwhile, Bartle Bogle Hegarty is seeking to follow Publicis' example by appointing a media communications specialist.
Unity's most recent win was a project from the publisher Hachette Filipacchi to create communications strategies for its flagship magazine brands Elle and Red.
Last year, the media shop experienced a series of major personnel changes. Morris left to join the Publicis Group in the new role of chief strategic officer. His hiring was seen as part of a growing recognition that media should be at the heart of agency thinking. A month later, the former ITV chief executive, Richard Eyre, joined Unity as an associate partner.
No one at JWT or Unity was available to comment.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the Forum here.