NEW YORK (Reuters) - Three private buyout funds have joined Cerberus Capital Management in exploring the possibility of bidding against billionaire investor Warren Buffett in an effort to acquire Clayton Homes Inc., a spokesman for the maker of manufactured homes said on Friday.

The Blackstone Group, Texas Pacific Group, Credit Suisse First Boston's buyout arm and Cerberus, a New York-based buyer of distressed assets, have all signed confidentiality agreements to conduct due diligence on Clayton Homes's books, said Carl Koella, a company spokesman.

However, it remains unclear at this point exactly how the relationships between the four buyout funds will work out, several sources familiar with the situation said on Friday.

They could ultimately team up for one bid, or decide to bid or walk away from the situation separately.

Combined, the four funds possess significant financial muscle, but it remains uncertain if any of them will attempt to trump Berkshire Hathaway Inc.'s existing $1.7 billion agreement to acquire Clayton Homes.

Clayton last week postponed a vote to approve the offer from Berkshire, a conglomerate controlled by Buffett, to give Cerberus and any other interested buyers time to review its books and make a competing bid.

Cerberus, CSFB and Texas Pacific Group all declined to comment. Blackstone did not return a call seeking comment.

The interest by the buyout funds was first reported on Thursday by the Knoxville News Sentinel in Tennessee.

Clayton Homes' shareholders are due to reconvene on July 30 to vote on the Berkshire bid, so time is of the essence for the funds. Buffett has vowed not to raise his offer any further.

Buyout funds are increasingly forming coalitions when bidding for large acquisitions, aiming to spread out deal risk among multiple firms and improve their competitive stance against strategic buyers, who typically can afford to pay more.