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Lindsay Lohan's Machete had a hard time knifing its way to the top during its opening weekend.

George Clooney's thriller The American nabbed the top spot with an estimated $13 million, just ahead of last week's box office winner Takers, which brought in an estimated $11.5 million.

Machete -- which also stars Jessica Alba and Robert De Niro -- debuted at No. 3, pulling in an estimated $11.3 million. Despite its somewhat disappointing ticket sales, Lohan says she's still proud of her return to the big screen.

"Machete is in theaters today! Go check it out!" Lohan, 24, tweeted Friday. "I'm so grateful to be a part of such a wonderful cast & experience! It's such a blessing!"

Still, a source tells that director Robert Rodriguez didn't want the troubled actress -- who was recently released from post-jail rehab -- to promote the film at its Aug. 25 premiere in L.A.

"He was frantically trying to track down her manager to make sure she didn't go," says the source.

Though a 20th Century Fox rep says it's "not true," the source tells Us, "She wasn't welcome there."

Compared to Lohan's last film, Labor Pains -- which debuted on ABC Family before it was sent directly to DVD -- Machete's debut is a notable improvement in the recovering actress' film career.

"Its a beautiful day in L.A. to have a hit film!" she tweeted Sunday. "Congrats to all of the cast, crew & production team of Machete! Danny Trejo is fantastic."