NEW YORK, DEC. 24 -- Takeover strategist Carl Icahn is threatening to disrupt Texaco Inc.'s settlement of its multibillion-dollar feud with Pennzoil Co. by suggesting he will propose his own bankruptcy reorganization for the oil giant.

The surprise suggestion by Texaco's largest shareholder, disclosed in a filing with the Securities and Exchange Commission late Wednesday, also said unidentified parties had approached Icahn to express interest in buying part or all of the nation's third-largest oil company.

"Texaco should either undergo a serious restructuring or be sold," Icahn said.

Texaco denounced Icahn's latest move, which came a few days after the company settled Pennzoil's historic $10.3 billion court judgment by agreeing to pay the smaller rival $3 billion in cash.

The settlement was part of a plan reached after exhaustive wrangling to extricate Texaco from court protection under Chapter 11 of the federal bankruptcy law, which it sought in April because of the Pennzoil judgment.

Industry analysts and Texaco insiders portrayed Icahn's move as a pressure tactic aimed at forcing management to scrap antitakeover provisions in the company's charter and give him a more powerful role in Texaco's fate.

They did not rule out the possibility that Icahn's ultimate goal was a takeover of Texaco. The financier controls 12.3 percent of Texaco's 242.8 million shares outstanding.

"In today's environment, if somebody comes up with something real good, shareholders go with it," said Jack Aydin, who follows Texaco for the securities firm McDonald & Co. "If I were management, I'd be thinking twice."

A Texaco source close to the settlement process, who agreed to discuss the matter only if not identified, said that if "Icahn were to float another plan, all other elements are out of the story. It would really throw the whole thing into disarray."

Texaco said in a statement from its White Plains, N.Y., headquarters that "any filing of a competing plan of reorganization in the current bankruptcy proceeding would be obstructive and counterproductive to Texaco's efforts to move quickly with a plan of reorganization and subsequent restructuring that will improve shareholder value."

The company's antitakeover provisions "enable Texaco's shareholders to receive fair value for their investment in the company, and the provisions protect the shareholders from attempts by any raider to obtain control of the company for less than full market value," the statement said. "These provisions are especially important for a company emerging from Chapter 11 when there is potential vulnerability."

In Houston, Pennzoil spokesman Robert Harper did not return calls to his office and home seeking comment.

Icahn also did not return calls. But a source close to Icahn, who spoke on condition of anonymity, said the financier wanted Texaco to abandon staggered terms for its directors and require a vote of only 10 percent of company shares to call a special stockholders meeting. With his 12.3 percent stake, that would enable him to call a special meeting at any time.

Texaco's shareholders committee, which played a crucial role in reaching the Pennzoil settlement last weekend, was not informed of Icahn's SEC filing, said Dennis O'Dea, the committee's lawyer.

O'Dea said he thought it highly unlikely Icahn would propose a rival reorganization plan, partly because of the procedural hurdles. Besides winning two-thirds approval in a shareholder vote, any plan also must be sanctioned by U.S. Bankruptcy Judge Howard Schwartzberg, who has been overseeing Texaco's affairs.

O'Dea also said that if Icahn proposed a competing plan, it would almost certainly provide for the same $3 billion payment to Pennzoil, which has indicated a desire not to become embroiled in any fight between Texaco shareholders and management.

"Pennzoil wants to get paid," O'Dea said.

On the New York Stock Exchange today,Texaco stock rose 62 1/2 cents a share to $38.62 1/2, and Pennzoil rose 12 1/2 cents a share to $74.75.

The Texaco-Pennzoil feud dates back almost four years, when Texaco acquired Getty Oil Co. after Pennzoil already had an agreement to acquire parts of Getty.

A Texas jury ruled in 1985 that Texaco unfairly sabotaged Pennzoil's plans, and awarded Pennzoil a record judgment that totaled $10.3 billion with interest prior to the settlement Dec. 19.