The Sirius and XM satellite radio providers will make an official announcement later today about a planned merger following a weekend of around the clock negotiations. The New York Post reports that details will be released at a conference in Washington D.C., and according to a source close to the deal, antitrust issues may still prevent the final merger from being approved.

If the deal is struck, XM Chairman Gary Parsons is likely to remain as Chairman for the combined group, while Sirius’ Mel Karmazin will fill the CEO position. The combined company would have roughly 12 million subscribers and would save both firms close to $7 billion per year.

Initial rumors about the deal popped up in mid-2006, with both Karmazin and Parsons admitting a merger would be necessary to combat the growing competition from conventional radio, online radio and downloaded music.