Dow Jones & Co.'s (NYSE: DJ) union has enlisted billionaire Ron Burkle to explore alternatives to News Corp.'s (NYSE: NWS)$5 billion take over bid in an effort to ensure editorial independence at the Wall Street Journal.

Burkle's Yucaipa Cos. agreed to advise the union on Tuesday, according to the Independent Association of Publishers' Employees, which represents 2,000 employees of New York-based Dow Jones.

The union is stepping up efforts to block a sale to News Corp. chief Rupert Murdoch, a day after the Bancroft family met with him to discuss his bid.

In response to concerns, Murdoch has offered to create an independent editorial board for the Journal, the newspaper with the second-largest US circulation. He also offered the Bancrofts a seat on the News Corp. board.

The Bancrofts, who have a 64 percent controlling interest in Dow Jones, described the meeting with Murdoch as ‘constructive.’ Murdoch issued a similar statement. The Bancrofts had initially rejected Murdoch’s bid in early May.

It is unclear whether Burkle will solicit bids from other buyers, or offer one himself. He

has been unsuccessful in recent attempts to buy newspapers.

Yucaipa, working with the CWA union, was outbid for the Philadelphia Inquirer and Philadelphia Daily News last year. The seller, McClatchy, Inc., accepted a $515 million offer from a group led by local businessman Brian Tierney instead.

Earlier this year, Burkle tried to buy Tribune Co., the second- largest U.S. newspaper company, in a partnership fellow Los Angeles mogul Eli Broad. Tribune rejected their bid and is selling the company to real estate billionaire Sam Zell.

Shares of Dow Jones were nearly flat in mid-day trading on the New York Stock Exchange, rising 2 cents, or 0.03 percent to $60.52.