NEW YORK (CNN/Money) - Lawyers for EchoStar Communications and Hughes Electronics have asked the Federal Communications Commission to delay judgment on their proposed merger because they are making "major revisions" to the pact.

In a letter to FCC Chairman Michael K. Powell dated Monday, the two companies did not detail these major revisions that they are apparently discussing with antitrust regulators.

But the companies may have reason to compromise. A series of published reports have said that federal regulators are poised to block the proposed purchase of Hughes Electronics (GMH: Research, Estimates) by the nation's other major satellite television provider, EchoStar Communications (DISH: Research, Estimates), amid worries that the $18 billion deal will be anti-competitive.

The companies aid they plan to submit a proposal on the deal before an Oct. 28 meeting with the Department of Justice. EchoStar and Hughes also asked for a public hearing on the matter.

The request comes as both the Wall Street Journal and USA Today report that the FCC is set to vote to block the deal, possibly this week.

The FCC is worried that the EchoStar-Hughes combination would create a monopoly over customers in areas not served by cable television, according to USA Today.

EchoStar executives have argued that combining the two companies is the only way to effectively compete with major cable television operators. Cable television has been going through its own consolidation, with Comcast Corp. (CMSCK: Research, Estimates) agreeing to buy the broadband operations of AT&T (T: Research, Estimates), the nation's largest cable television provider.

Rejection by the FCC would be a blow not only for EchoStar but for General Motors Corp. (GM: Research, Estimates), which owns Hughes (GMH: Research, Estimates), whose largest unit is the DirecTV satellite television service. GM, which faces an underfunded pension fund due to stock market declines, had expected to use proceeds from the sale to strengthen its balance sheet and make necessary pension contributions.

EchoStar faces paying a $600 million breakup fee if the deal is blocked.