With the summer season entering its home stretch, an oddball pair of hard-to-define R-rated comedies seek to strike sparks at the box office this weekend.

Universal is unwrapping “American Wedding” at 3,174 altars. Studio is emphasizing the romance in a somewhat less raunchy culmination to the “American Pie” trilogy in hopes of overcoming possible sequel fatigue, while still attracting pic’s core target crowd of teens and young adults.

Sony/Revolution is hoping the combined star power of Jennifer Lopez and Ben Affleck as romantically involved assassins can overcome considerable downbeat buzz for “Gigli,” which opens at 2,215 engagements.

Expectations are definitely higher for “Wedding,” given the return of the same cast that generated solid perfs for 1999’s “Pie” and 2001’s “Pie 2.” The original was a surprise hit with legs that opened at $18.7 million and cumed $101 million; the latter debuted impressively with $45 million and finished with $145 million.

Wary about sequels

But U execs have suggested caution, citing the summer’s mixed record so far on sequels. Last weekend’s leader, Miramax’s “Spy Kids 3D: Game Over” outperformed forecasts with $33.4 million but Par’s “Lara Croft Tomb Raider: The Cradle of Life” debuted in fourth with a modest $21.8 million, two years after the original cumed $131 million; many other sequels that opened well have suffered steep subsequent drop-offs.

“You can’t get away from the fact that people are talking about sequel-itis during this summer,” said distrib chief Nikki Rocco. But she also noted that “Wedding” is clearly aimed at attracting more femme support by focusing more on the romantic comedy angle than its coming-of-age predecessors.

“This film is really a validation of the relationship,” she added.

By comparison, prospects are murky at best for “Gigli” despite the massive publicity that has engulfed it and real-life romance between Affleck and Lopez in recent months. Revolution partner Tom Sherak admits the story — combining elements of drama, caper, comedy and romance — is a tricky sell and credited the stars with actively promoting the pic.

‘Offbeat curveball’

“People are looking to go see an adult comedy and this is an offbeat curveball,” he said.

A trio of holdover pix figure to be significant players: the soph seshes of “Spy Kids 3D: Game Over” and U’s “Seabiscuit,” which is adding 432 engagements to go into 2,421, along with the fourth outing of Disney’s “Pirates of the Caribbean: The Curse of the Black Pearl,” which had cumed more than $187 million on Wednesday. Rocco said good word of mouth plus strong midweek perfs by “Seabiscuit” — with more than $8 million during Monday-Wednesday — dictated the expansion.

If “Wedding” and “Seabiscuit” perform well, U has a shot at finishing the summer with five pix topping $100 million, joining “Bruce Almighty,” “The Hulk” and “2 Fast 2 Furious.”

The weekend will also serve as a signal of whether the 2003 summer will top last year’s record-setting total. The current summer held a lead of less than 1% at the end of the previous frame.

But the year-to-year comparison may be tough since the first weekend of August 2002 generated an impressive $156.5 million, according to BO tracker NielsenEDI, led by $60.1 million for “Signs” debut, followed by $142 million in the following frame.

“The weeks in early August can produce solid revenues,” said Nielsen EDI VP Dan Marks. “If there is viable product, people are good to go.”