AT&T Inc. will ask a federal judge in Washington today to eliminate Sprint Nextel Corp.'s lawsuit that aims to block its takeover of T-Mobile USA Inc.

Sprint, along with Cellular South Inc., claim that AT&T's proposed merger with T-Mobile will cause an unfair advantage in the mobile market. AT&T responded to the suit saying that an antitrust case is meritless when brought by competing companies rather than consumers.

If the judge decides in AT&T's favor, however, Sprint could still assist in the U.S. Department of Justice's (DOJ) case against AT&T. Like Sprint, the DOJ sued AT&T in August for violating antitrust law, and asked U.S. District Judge Ellen Segal Huvelle to block the company from merging with T-Mobile.

In addition to lessening competition in the mobile service market, the DOJ alleged that if AT&T succeeded in acquiring T-Mobile, the company would increase prices and provide lower-quality service.

Jeffrey Jacobovitz, an antitrust lawyer with McCarthy, Sweeney & Harkaway, told Bloomberg that even in a lost case, Sprint could help the DOJ by providing the government with information for their case and filing amicus briefs.

Sprint also could aid the DOJ's case by disclosing information regarding evidence and arguments that AT&T uses in this case, the government said in a court statement.

Update: U.S. District Judge Ellen Huvelle heard oral arguments from both AT&T and Sprint on Monday but did not issues a ruling. For more, read coverage in the Wall Street Journal.

Click here for more on the DOJ's case against AT&T.