CEO of Nielsen, Mitch Barns and wife, Sharon Barns attend Nielsen Hosts Pre-GRAMMY Celebration Connecting Media Brands and Entertainment on February 7, 2015 in Los Angeles, California.

Nielsen Holdings will expand a review of strategic alternatives to include a sale of the entire TV ratings company, the firm told Reuters on Tuesday, after coming under pressure to do so from hedge fund Elliott Management.

Nielsen, best known for providing audience figures that are used to determine advertising rates for TV commercials, has been seeking to adapt to the media industry's shift to digital advertising and video consumption on mobile devices.

Nielsen said in the statement it was working with investment banks JPMorgan Chase and Guggenheim Securities, as well as law firm Wachtell, Lipton, Rosen & Katz, on an "expanded" review of strategic alternatives.

The company had said previously it was only exploring a sale of its "buy" segment, which provides marketing data on what customers purchase, and not its "watch" segment, which offers viewership and listenership data and analytics across television, radio, online and mobile devices.

The expanded review includes an assessment of a broad range of options, including continuing to operate as a public, independent company, a separation of either Nielsen's buy or watch segment, or a sale of the company, Nielsen said, cautioning that no deal is certain.

Elliott unveiled a stake in Nielsen last month and called on the company to explore a sale in its entirety.

The hedge fund declined to comment on Tuesday. Nielsen faces competition from start-ups using automated content recognition (ACR) to track viewing habits via mobile devices and smart TVs. It acquired Gracenote in 2017 in a bid to bolster its ACR capabilities.

As viewer habits change, Nielsen has also made a move to cover shows watched on online streaming services, via platforms such as Netflix or via games consoles.

Nielsen is heavily indebted, the legacy of a leveraged buyout in 2006 by six private equity firms; Carlyle Group, Blackstone Group, KKR & Co, Thomas H. Lee Partners, AlpInvest Partners and Hellman & Friedman.

They took Nielsen public in 2011, and the company now has a market capitalization of $9.4 billion and total debt of $8.66 billion.

Nielsen has received some interest from private equity firms for a new leveraged buyout of the entire company, according to people familiar with the approaches who requested anonymity to discuss them.

However, such a deal would represent one of the biggest leveraged buyouts of recent years, and it is unclear whether such a transaction can be put together.

James Attwood, executive chairman of Nielsen's board, is leading the review, the company said.

Attwood is a managing director at Carlyle and the former head of its global telecommunications, media, and technology group, according to the company's website.

Nielsen said in July that is CEO Mitch Barns will step down at the end of the year. Attwood has been leading the search for Barns' successor.