Motorola Inc., which had been the largest shareholder in Nextel Communications Inc., said yesterday that it has sold 23 percent of its 108 million shares in the Reston-based wireless telephone company, pocketing a $250 million pretax gain.

The announcement shook Nextel's stock price, which seesawed throughout the day to close down 26 cents at $13.22. But Motorola, which supplies Nextel's walkie-talkie-like phone handsets, took pains to say that it still had "great confidence in the ongoing success of Nextel."

Motorola also said it locked in gains on up to another 25 million of its Nextel shares by entering into "forward sale" contracts with several investment banks. The actual sales won't occur for another five years, the company said, but the contracts allow Motorola to protect itself against future Nextel price drops. When the actual sales occur, Motorola's stake in Nextel would drop to no less than 6 percent, the company said, assuming no other changes in Nextel's shares outstanding over that period.

Motorola "has 75 percent of their holdings still, and they're still extremely supportive," said Audrey Schaefer, a Nextel spokeswoman. Motorola, which is now the second-largest shareholder of Nextel stock, still has 83 million shares, or 9 percent of the company, and occupies one of 10 seats on Nextel's board of directors, she said.

Meanwhile, Standard & Poor's Corp. announced yesterday that it affirmed Nextel's B+ credit rating and improved its outlook on the company's ability to pay its debt to stable from negative. S&P said its action was based "on the company's solid operating performance in a highly competitive industry and lower financial leverage, despite substantial debt still on the balance sheet." Nextel had $12.5 billion in debt at the end of 2002.

"This is very much a Motorola-specific issue, but [also] a sign that Nextel is going to move away from Motorola" over time, said Craig A. Mallitz, an analyst with Legg Mason Wood Walker, the investment bank that is now the largest shareholder in Nextel. "It will be more of an operational relationship than a strategic one," he said.

Motorola, the world's second-largest maker of cell phones, engineered a financial turnaround last year, largely through cutbacks and restructurings. News that Motorola was selling some of its stake in Nextel, the fifth-largest wireless carrier in the United States, did not spark much concern among research analysts who follow Nextel.

"Motorola's sale of those shares does not dilute the stock, and it doesn't mean they give up their seat on the board," so it does not fundamentally change the relationship between the two companies, said Walter Piecyk, an analyst with Fulcrum Global Partners in New York.