An American man who flew to Canada to have sex with a 13-year-old girl has been sentenced to more than seven years behind bars.

Prosecutors in California had wanted Paul Binh Do jailed for nine years on the grounds that he had caused the Calgary teen, who sent him nude videos, severe distress, and had tried to cover up his crimes.

Do, 30, of Garden Grove, Calif., had pleaded guilty to travelling with the intent to engage in illicit sexual conduct and being in receipt of child pornography. He was sentenced in Santa Ana, Calif., to 87 months in a federal prison on each count, to be served concurrently.

United States District Judge David Carter recommended prison authorities conduct a mental-health evaluation of Do and provide "all necessary treatment."

"The defendant shall participate in a psychological counselling or psychiatric treatment or a sex offender treatment program," Carter said in his sentencing judgment.

Nude photos and video exchanged

Do will be on supervised release for the rest of his life once he leaves prison, will have to provide a DNA sample, and register as a sex offender, Carter ruled.

According to court documents, Do, who was then 26, began communicating with 13-year-old M.F., of Calgary, in September 2013, when she posted online that she wanted to meet guys.

The two pursued contact via social media and text messaging, and he asked her to be his girlfriend. They exchanged nude and sexually explicit photos and videos, and he persuaded her to engage in "prohibited sexual conduct," according to an agreed statement of facts.

The first-time offender with a university degree in business administration flew to Calgary in May 2014 to have sex with M.F. on what would have been her 14th birthday. Canadian authorities arrested him on arrival. Do then called the girl and asked her to tell authorities that she had lied to him about her age, records show.

'Operation Predator'

Authorities found explicit images of the girl on Do's computer and phones. Investigators also found conversations with five other girls that were sexual in nature. In one case, he discussed flying to London to visit a girl who had identified herself as a 15-year-old, court records show.

Do also admitted to breaching bail conditions by visiting parks on at least 12 separate occasions. He will be required to stay away from school yards, parks, public swimming pools, playgrounds, youth centres, or any other places

primarily used by those under 18, and may not generally communicate with anyone under 18 without supervision.

The court waived any fines on the grounds that he would not be able to pay them. Authorities had already confiscated his computer and cellphones and Carter ordered those items forfeited.

The investigation by U.S. Homeland Security that snared Do was part of an international initiative begun in 2003 — dubbed "Operation Predator" — aimed at protecting children from sexual predators.

The initiative resulted in the arrests of more than 14,000 people for crimes against children.