The corporations said they agreed to suspend the registration rights process associated with AT&T's (T) stake in Time Warner Entertainment "for a short period of time" so that the two companies can pursue "discussion of an alternative transaction" with Comcast (CMCSK) A Comcast spokesperson could not be reached early Tuesday morning.

The move marks the demise of another prospective, billion-plus dollar deal in the barren market for initial public offerings.

Such big IPO ships had been big enough to sail despite the stormy market, but lately conditions have been too rough even for them.

Earlier this month, Merck (MRK) pulled plans to offer its Medco unit IPO after a series of problems. See full story. Since then, only a couple of IPOs, of any size, have been able to make it out the door. No deals are on tap for this week.

For AOL Time Warner and AT&T, the move marks the latest in a series of corporate machinations.

AT&T is in the process of breaking itself up and plans to shed its media properties.

AOL Time Warner is facing historically low stock prices and has recently shed its chief operating officer, Robert Pittman.

The AT&T unit in question includes Time Warner's significant cable TV business as well as premium cable channel HBO and parts of Warner Entertainment.

AT&T and AOL Time Warner (AOL) "gave no assurances" that the discussions would result in a transaction. AOL Time Warner spokesman Ed Adler confirmed that company officials had been publicly talking about an IPO for the unit.

He gave no timetable on when any possible deal with Comcast would take place.

The two companies said they do not intend to provide updates unless they reach a definitive agreement or return to IPO process.

For the time being, AT&T and AOL Time Warner have asked Banc of America Securities "not to deliver an opinion on how much AT&T's stake in Time Warner Entertainment is worth and how much of that stake could be sold in a public offering."

Shares of AT&T rose 5cents to $9.79 on Tuesday. AOL Time Warner gave up 5 cents to $11.53 and Comcast rose 19 cents to $20.79