Phillips Petroleum Co., conceding that, as expected, shareholders had defeated a plan to recapitalize the company, yesterday unveiled a new proposal to exchange $4.5 billion worth of debt securities for about half of the company's stock.

Like the previous plan, the proposal clearly is an attempt to increase shareholder value in the company, an action the company's management hopes will deter an attempt by New York financier Carl C. Icahn to take control of Phillips.

Icahn, who had led opposition to the earlier proposal and had said he would begin a $8.5 billion offer to buy out Phillips if it was defeated, could not be reached for comment last night.

"Many of our shareholders wanted a different type of transaction and our new proposal is designed to deliver the value we believe they want," Phillips Chairman William C. Douce said in a statement issued yesterday evening from the company's Bartlesville, Okla., headquarters. "We believe it is clearly superior to the heavily conditioned scheme proposed by the Icahn group."

Under the new plan, which need not be approved by shareholders, Phillips will offer debt securities with a face value of $62 a share for 72.5 million of its 154.6 million shares. Remaining shareholders will be rewarded with a higher dividend rate, and Phillips estimated that the combined value of dividends and interest from the debt securities would be worth about $5.48 per share, more than twice the current dividend of $2.40. The company also plans, pending shareholder approval at this year's annual meeting, to issue a further dividend of preferred stock and to split its common stock 3-for-1. In addition, Phillips will sell $2 billion in assets to help pay for the package.

It was not immediately known how Wall Street analysts would value the new plan, and the total value of the package could be determined by market forces to be worth less than the debt securities' face value of $62 a share. Phillips stock closed Friday at $49.25, unchanged from the previous day's price.

Disputes over the value of the previous proposal -- a combination of $60-face-value debt securities and other inducements said by Phillips to be worth $53 a share but valued by market experts and Icahn at much less than that -- are believed to be the reason Phillips shareholders voted down the earlier plan.

Phillips has been under siege for three months, since a group led by Mesa Petroleum Co. Chairman T. Boone Pickens Jr. tried to take over the company. Phillips made peace with Pickens in an agreement that included the recapitalization program, only to have Icahn challenge the plan with his offer for the company.