Comcast and General Electric have extended the deadline for closing the merger deal that was inked a year ago.In an SEC filing Friday, Comcast said that the sides triggered a provision to extend the deadline by three months, or to March 3. The original deal, unveiled Dec. 3, 2009, also gives them the option to trigger another three-month extension. Comcast and GE execs have said they’re confident that the merger deal, which calls for Comcast to acquire 51% of NBC Universal from GE, will receive regulatory approval by year’s end. The FCC and Justice Dept. have been reviewing aspects of the transaction for months. The FCC’s 180-day time frame for approving the merger ended late last month, but there’s no official word yet from the commission on a timetable for a decision.