An attorney for actor John Stamos denies the "Full House" and "ER" star had a romantic fling with a 17-year-old girl who six years later is accused of scheming to bilk him of hundreds of thousands of dollars by threatening to sell compromising photos to the tabloids.

A defense lawyer made the allegation Monday during opening arguments in U.S. District Court as Allison Coss and Scott Sippola went on trial, charged with conspiracy to commit extortion. Coss, 24, and Sippola, 31, both of Marquette, are accused of conspiring to extort $680,000 from Stamos by telling him they had photos of him with cocaine and strippers — pictures prosecutors contend don't exist and that two FBI agents testified they did not find while searching the defendants' house after their arrest.

Stamos, 46, is expected to testify during the trial, which resumes Tuesday. But it's unclear if he will address the defense's claim that he had a romantic encounter with Coss when she was a high school student on a spring break trip to Florida in 2004.

The presiding judge last week ruled that testimony about whether Stamos had an intimate relationship with Coss would not be allowed. Opening statements are not testimony and cannot be considered by jurors as evidence but allow attorneys to outline the case they will present.

Stamos declined to comment to The Associated Press after Monday's opening statements. But his attorney, William Sobel, issued a statement through publicist Matt Polk denying the defense's claims.

"The allegations made today in the courtroom by the defendants' attorneys during opening statements will not be proven because they are simply untrue," the statement said.

Defense attorney Sarah Henderson and Assistant U.S. Attorney Maarten Vermaat agreed in their opening statements that Coss and Stamos met in Orlando, Fla., in 2004 — shortly after Stamos had separated from his wife, actress and supermodel Rebecca Romijn. The couple divorced the next year.

Henderson said Stamos, now 46, noticed Coss and another girl at a club, asked friends to bring them over and later invited the star-struck teens to his hotel room. Stamos ordered a drink for Coss even after she told him she was 17, Henderson said.

Two women who worked as strippers eventually showed up in the room with a bag of cocaine, she said, and Coss and her friend took a picture of Stamos bending over a table where the drugs had been laid out.

Henderson said Stamos and Coss later kissed on a bed and got into a hot tub together after Stamos undressed and Coss stripped to her underwear. She said Stamos offered to perform oral sex on Coss, but she declined. Florida law makes it a second-degree felony for someone 24 or older to have oral sex with anyone 16 or 17 years old.

Stamos eventually became frustrated, broke a bedpost with his hand and left the room before apologizing and inviting Coss to spend the night, which she did, Henderson said.

For the next few years, they maintained a "flirty kind of relationship" by e-mail, Henderson said.

Vermaat said the two exchanged e-mails "with some regularity" but did not discuss details of the alleged 2004 encounter.

Stamos received two e-mails last fall from a "Jessica T" who claimed she was pregnant and Stamos was the father, Vermaat said. Later came a series of e-mails from a "Brian L" describing allegedly compromising photos and saying they would be sold to tabloids if Stamos did not buy them for $680,000.

Prosecutors contend Coss and Sippola sent the e-mails.

Henderson acknowledged Coss was "Jessica T" but described the e-mails as a ruse to test Stamos' reaction in hopes of determining whether he was preying on young girls.

Stamos contacted the FBI, Vermaat said. Two agents testified about a sting operation that ended with Coss and Sippola's arrest at K.I. Sawyer International Airport near Marquette, where an agent posing as a Stamos representative had promised to leave a bag of cash.

"This is really just a get-rich-quick scheme that is based on lies and betrayal," Vermaat told the jury of eight men and four women.

Defense attorneys said their clients had a right to try to sell photos to Stamos and considered it a legitimate business transaction, not a crime.