Hayne declined to answer questions on the December 2015 matter when he fronted the media after returning to NRL club Parramatta on Wednesday for the first time since 2014.
His lawyers later revealed in a statement that he had made contact with the plaintiff, while Hayne said he had told his US legal representatives to have the matter resolved "as quick as possible" after it was revealed a civil suit had been launched last month.
"I confirm that I unequivocally and vehemently deny the allegations made against me and I will be vigorously defending the matter," Hayne said.
"I have the utmost faith in the United States justice system and have left this matter with my legal team."
Hayne's lawyers said they were yet to be served with papers for the civil proceedings over the alleged incident, which was said to have occurred during Hayne's stint in the NFL.
Hayne's US lawyer, Mark Baute, was confident he would be cleared.
"Mr Hayne is innocent and will ask a United States jury to find him innocent," Baute said.
"There is no objective evidence of any sexual assault in this matter and the lawsuit lacks merit.
"Mr Hayne and I look forward to the day when a jury can find him innocent."
Baute was the trial lawyer who successfully defended NBA star Derrick Rose over rape claims in a federal civil case in 2016.
According to US court documents, Hayne was interviewed by Santa Clara police in May of 2016 in relation to claims made by a woman over an alleged incident the previous December.
In October 2016 the woman, known as Ms V, was told by police that there was insufficient evidence to proceed with a criminal case.
However she is now pursuing the two-time Dally M winner on claims of sexual battery, gender violence, infliction of emotional distress and negligence in a civil suit.
Hayne, 29, returned to his childhood club at the Eels from the Gold Coast this summer, and said he was yet to talk to Parramatta management about the matter.
He also deflected questions on whether he had informed the then-NRL owned Titans he was the subject of an investigation when he signed in August 2016, however the club has previously claimed they were not told.
Hayne quit his NFL stint with the San Francisco 49ers in the same month he was spoken to by investigators, but denied his departure was related to the incident.
He also said the claims hadn't taken away from his dream of playing in the NFL, but hit out at media for following him to his pre-planned trip to Israel and attempting to speak to his family in the past fortnight.
"It's been tough for them - it's been pretty emotional just seeing them get ambushed," Hayne said.
"That sort of thing was pretty disappointing and hard to watch and listen to.
"I don't think you can describe the feeling (of learning of the case). You've just got to go through it and let justice take its course."