Some of the biggest media and telecommunications companies covet DirecTV, which provides wireless television service and high-speed wireless Internet services. DirecTV is part of Hughes Electronics Corp., a subsidiary of General Motors.

Shares of both General Motors and Hughes shot up Thursday after a report on CNBC that News Corp. and Liberty Media were considering a takeover bid for General Motors in an effort to get control of DirecTV.

News Corp. quickly issued a statement saying the report was "entirely false and without merit," but the unabated market speculation highlights the fact that GM, which declined comment, is sitting on a very valuable asset.

"Hughes fits nicely with many of the other media and telecommunications companies, but I am of the opinion that GM would like to keep control of Hughes and doesn't want to let it go," said Mike Kagan, portfolio manager of the Salomon Brothers Fund, which owns 100,000 shares of Hughes.

When GM bought Hughes in 1985, GM controlled about 41 percent of the U.S. automotive market. GM executives acquired Hughes to help offset the cyclical troughs of car sales.

They couldn't have guessed that Hughes' satellite business would someday be on the leading edge of Internet and television technology. Today, GM's share of the car market has shrunk to 29 percent, and Hughes' market value (more than $60 billion) is greater than General Motors', the world's largest automaker (about $54 billion).

Earlier this year, Hughes sold its satellite manufacturing business to Boeing in order to focus on its fast-growing DirecTV wireless television service and new Internet ventures.

While analysts would not rule out a bid for General Motors, any unwanted bid would meet huge opposition. GM has tremendous clout in Washington as well as on Wall Street, and the company has a strong labor union.

"The logistics are quite difficult, and it certainly wouldn't be done without a fight," said Nicholas Lobaccaro, an analyst with Lehman Brothers.

Some precedent exists; in 1995, Kirk Kerkorian made a hostile bid for Chrysler Corp. Kerkorian backed down after an ugly 10-month battle, though he made Chrysler take action to boost its flagging stock price.

General Motors, for its part, has tried to unlock the value of Hughes, which trades as a tracking stock. A tracking stock reflects the value of a specific corporate line of business.

The auto manufacturer, which holds a controlling stake in Hughes, recently said it would buyback about $9 billion of GM shares using Hughes' stock. This would give its shareholders more of the benefit from Hughes' shares, which have risen 30 percent this year compared with GM's 12 percent price appreciation.