Comic-Con International has sold out, two months ahead of last year's event, after the remaining Sunday memberships were purchased late this afternoon.

The early sellout comes as no surprise, as four-day passes disappeared in November, while Saturday memberships were gone by mid-December, almost four months earlier than those for the 2009 convention. The other two days weren't far behind, with Friday selling out in January and Thursday going the way of the dodo just two weeks ago.

The news arrives as Anaheim and Los Angeles step up their efforts to lure Comic-Con from San Diego, where the event long ago outgrew the city's convention center, resulting in a capping of attendance at about 125,000.

Comic-Con's contract expires in 2012, but the San Diego Convention Center Corp. is seeking to extend the agreement an additional three years, in part, by securing commitments from three waterfront hotels to provide for free about 300,000 square feet of meeting space from 2013 to 2015. The San Diego Convention Center has 615,700 square feet of exhibit space, compared to the Los Angeles Convention Center's 720,000 square feet and the Anaheim Convention Center's 815,000.

There's also an effort by San Diego to increase the number of dedicated convention hotel rooms from 7,000 to 14,000, which would give the city a great advantage over Anaheim and L.A. (The former has about 4,500 hotel rooms within walking distance of its convention center, the latter just 2,000.)

Comic-Con begins July 21 with Preview Night, and continues through July 25.