In the lawsuit, plaintiff Margie Carr charges that Stallone physically and sexually assaulted her in a gym in the Los Angeles suburb on February 28, 2000.
The lawsuit alleges that Stallone "forcibly pinned" Carr against a wall, tore her clothes, pushed her onto a sofa and "attempted to forcibly have sexual intercourse" with her.
Stallone's lawyer, Marty Singer, on Wednesday called the charges "purely fictional and totally without merit".
He said Carr had sold her story to the Globe supermarket tabloid in January, before filing the lawsuit on February 26.
"She wanted to marry my client and wanted him to leave his wife," he added. The star of "Rocky" and the "Rambo" trilogy has been married to model Jennifer Flavin since 1997, and the couple has two daughters.
"The problem is that, in America, anybody can sue anyone on claims, whether false or not," Singer said.
"Our belief is that she filed this lawsuit to sell another story to the tabloid," he said. "We were told that she and her lawyer were attempting to sell a story to the European tabloids." Carr is seeking unspecified damages. - Sapa-AFP