Phillips 66 (PSX) asked its shareholders Tuesday to reject activist investor Elliott Investment Management's attempt to change the leadership and strategy of the company, according to a definite proxy statement.

The energy company described Elliot as "an activist hedge fund pushing an aggressive short-term agenda," who is seeking a "quick win by breaking up the company, based on inflated and unrealistic assumptions."

Elliot has accused Phillips management of underperformance and has called for a sale of non-core assets and a "refresh" of the leadership team.

The company urged shareholders to vote for its slate of director nominees at the annual stockholders' meeting on May 21.

Shares were 3% higher in recent premarket activity.