The family of Harry Dunn will only meet the American woman involved in the crash that killed him if he agrees to return to the UK, their spokesman has told Sky News.
Radd Seiger said the condition was a "non-negotiable red line in the sand" as Harry parents, Charlotte Charles and Tim Dunn, arrived in New York in the hope of meeting Anne Sacoolas.
Mrs. Sacoolas, the wife of a US diplomat, has previously said she wants to meet the pair to "express her deepest sympathies and apologies".
Harry, 19, edited when his motorbike collided with a car outside an RAF base in Northamptonshire in August, before Mrs. Sacoolas returned to America after being granted diplomatic immunity.
The Foreign Office says she no longer has diplomatic immunity because she has returned home.
After Harry's parents arrived in New York on Sunday, Mr. Seiger told Sky News that the conditions for the potential meeting were yet to be agreed but it was hoped it would take place later this week.
"It's important to make it clear, it's all about her coming back," he said.
"For the family, the non-negotiable red line in the sand is that she must return to the UK and face the consequences and I am awaiting a response to that.
"There's not much point in meeting and having fun if that commitment isn't there."
After Mrs. Sacoolas said she wanted to meet Harry's parents to apologize, the teenager's mother told Sky News that "sorry doesn't cut it".
"That's not really quite enough," Ms. Charles said.
"But I'm still really open to meeting her, as are the rest of us. I can't promise what I would or wouldn't say, but I certainly wouldn't be aggressive."
Harry's parents had expressed anger and disappointment at how the UK government had handled the case following a meeting with Foreign Secretary Dominic Raab.
But on Saturday they received a letter from Mr. Raab to say that Mrs. Sacoolas no longer has diplomatic immunity, meaning the case could now be taken forward by Northamptonshire Police.
Detective Superintendent Sarah Johnson told Sky News that the force is working with the Crown Prosecution Service and other agencies to progress its investigation – even though the suspect is not in the UK.
"The drivers that we are seeking do get involved with us after the original collision," she said.
"After the original meeting on 28 August, we were advised that diplomatic immunity be applied, which therefore prevented us from being able to otherwise progress the investigation."
She added: "We are really determined to make sure we can progress this investigation to seek the outcome that's correct and right for Harry and his family."
Ms. Johnson emphasized that the police were yet to name Mrs. Sacoolas as the suspect involved in the crash, and that the force was hoping for a "judicial outcome" to the case.
However Home Secretary Priti Patel has played down suggestions that Mrs. Sacoolas could be extradited from the US.
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She told The Andrew Marr Show: "The foreign secretary has been working with his American counterpart, he has been in touch with the US administration on this.
"It very much seems that the lady in question wants to start co-operating with the discussions and the investigations and I think that we should support that.
"We need to ensure that justice is done but obviously that co-operation with this investigation takes place. That is absolutely right."