A 40-year-old man from the US has been sentenced to 35 years in prison, after he groomed a 16-year-old girl from Sydney on social media to travel to New York for sex.

Key points: Missing Australian teenager found in New York with 40-year-old man

Missing Australian teenager found in New York with 40-year-old man Sean Price had started talking to the teen online in spring 2016

Sean Price had started talking to the teen online in spring 2016 Price sent the teen $US900 ($1,200) to fly to the US with the intention of engaging in sexual activity

The teenager's parents reported her missing from her home on Sydney's upper north shore in April last year, and she was found a month later with Sean Price in New York, where he was arrested.

Price was found guilty of four charges in December last year, including interstate and foreign enticement to engage in sexual activity, and attempted sexual exploitation of a minor.

The Federal Court in Brooklyn heard that Price had started talking to the teen online in spring 2016.

Evidence in the trial showed by January 2017, they spoke daily through messages on Facebook, where Price openly talked about the girl's age, and his desire for her to travel to the US and to engage in sexual activity with the teenager.

Price preyed on girl's 'vulnerability'

Messages showed Price and the girl also discussed her getting a fake passport, with Price offering to impersonate her father to help her through airport security in the United States.

When the teenager told Price she did not need parental permission to fly internationally, he replied: "So you coming to Papa?"

The court heard Price sent $US900 ($1,200) to the teenager to fly to Los Angeles before they drove cross-country to his home in Queens, New York.

Price admitted he and the teen were involved sexually during the trip and while they were living in Queens, until she was discovered by authorities and returned to her family in Australia.

"Price lured a teenage girl across the globe to satisfy his own sordid desires, taking advantage of her youth and preying on her vulnerability," Homeland Security Investigations Special Agent-in-Charge Angel Melendez said.

"These cases are a harsh reminder of the importance of educating our young people on the dangers of sexual predators on the internet."

US authorities praised the co-operation of the Australian Federal Police (AFP) and NSW Police.

Acting Commander Joanne Cameron, manager of the AFP's Victim Based Crime team, said the case was a reminder for parents to talk to children about their online activity.

"When our kids are online, we are helping them to discover the wealth of information out there - and this access to technology should never be discouraged. But what we would encourage is for parents to be alive to the risks and to educate themselves, and their kids, about them," Ms Cameron said.

Talk to your children about 'dangers' online

Detective Inspector Michael Haddow from the NSW State Crime Command Child Abuse and Sex Crime Squad implored parents to talk to their children about "the dangers of the online world".

"Our kids are our most valuable resource," he said.

"This is real, it's not just in the US, it's real here."

Detective Inspector Haddow said NSW Police had arrested dozens of men who turned up to locations believing they were meeting children for sex.

"Every day, there's a new app, a new way of children engaging with people online," he said.

"This is an extreme example of how far a child will go.

"Grooming is a very powerful thing, we are talking about children here, [it] doesn't matter if they're 14, 15, 16, they're vulnerable."