Fidelity, whose 2.5 percent stake makes it DuPont's sixth largest shareholder, has not publicly revealed what sort of compromise it was seeking. Yet its unusual intervention as peacemaker could influence other mutual fund investors in DuPont and pre-empt what could be this year's biggest battle over board representation.

In a filing with the U.S. Security and Exchange Commission last Wednesday, Trian disclosed that on March 11 it received a call from one of DuPont's largest stockholders encouraging Trian and the company to resolve the proxy contest and avoid a costly and disruptive conflict. It did not disclose the name of that investor, but those familiar with the matter said it was Fidelity, the second largest U.S. mutual fund company.

A Fidelity spokesman declined to comment. DuPont and Trian reiterated their positions, but declined to comment on Fidelity's involvement.

"Since 2009, DuPont has been executing a transformational strategy that is delivering superior results," a DuPont spokeswoman said.

"In direct contrast, Trian has a singular, value-destructive agenda to break up and add excessive debt to DuPont, which we believe would put shareholder value at risk," she added.

A Trian spokeswoman rejected the criticism.

"We have met recently with many of DuPont's largest stockholders and our ideas clearly resonate with them," she said. "We believe that Trian's presence on the board will help to drive sales, margins, and earnings growth at a company where EPS (earnings per share) is expected to be lower in 2015 than in 2011 for the fourth year in a row."

Trian, which owns a 2.7 percent stake in DuPont, is pushing for the appointment of four of its own directors at the company's annual shareholder meeting on May 13. The slate includes Trian's co-founder and Chief Executive Officer Nelson Peltz, who has requested a seat on the board since earlier this year.

DuPont, which has a market capitalization of $65 billion, named two of its own nominees, Ed Breen and Jim Gallogly, as directors last month. In an attempt to end the proxy war, the Wilmington, Delaware-based company has said it is prepared to accept one of the fund's nominees, but has refused to add Peltz to its board. [ID:nL3N0WP50E]

DuPont had said it would spin off its performance chemicals business. Peltz also wants the company to separate its volatile but cash flow-strong materials businesses from its nutrition and health, agriculture, and industrial biosciences divisions.

DuPont has rejected the proposal, stressing that keeping its businesses together would allow the company to benefit from its science platform, global scale, market access and brand.

SHAREHOLDERS DIVIDED

Over the past few weeks, both camps have been lobbying with DuPont's top 30 to top 40 investors, the sources said.

A Reuters poll of investors who hold about 48 million DuPont shares representing 5 percent of the company, found them split on Trian's board representation.

"We bought DuPont before this happened, and we do think this is, at minimum a distraction, at maximum a dislocation to the plan that is in place," said Robert Zagunis, managing director of Jensen Investment Management, which owns 1.8 million DuPont shares. "We want this to be resolved, and with DuPont winning the proxy."

Others disagreed. "We think the board needs to make decisions in the boardroom to maximize value. Trian brings one perspective for them," said Aeisha Mastagni, an investment officer for California State Teachers' Retirement System, which held about 3.6 million shares as of Feb. 28.

(Additional reporting by Tim McLaughlin in Boston; Editing by Greg Roumeliotis and Tomasz Janowski)

By Nadia Damouni and Mike Stone