Harry Dunn’s parents are set to meet Foreign Secretary Dominic Raab, ahead of the US secretary of state’s visit to the UK.
The parents of the teenage motorcyclist, who died in a hit-and-run last August, said they are hopeful the “vitally important meeting” will be “constructive and productive”.
The 19-year-old’s father Tim and mother, Charlotte Charles, are locked in a row with the Foreign Office over their claim that suspect Anne Sacoolas had diplomatic immunity.
It comes as Mike Pompeo, the US secretary of state, plans to meet Boris Johnson on Wednesday.
Mr Dunn was killed when his motorbike crashed into a car alleged to be driving on the wrong side of the road outside RAF Croughton, a US military base in Northamptonshire.
The US rejected an extradition request from the Home Office on Thursday, despite the Crown Prosecution Service charging the 42-year-old with causing death by dangerous driving.
A spokesman for the US State Department said if the extradition request was granted, it would render the invocation of diplomatic immunity a practical nullity and would set an extraordinarily troubling precedent.
Mr Dunn’s parents have said they expect the foreign secretary to make it clear in the meeting there will be “severe consequences” if the US government continues to refuse to return Mrs Sacoolas after their meeting on Monday.
Radd Seiger, spokesman for the Dunn family, told the PA news agency: “Harry’s parents are very much looking forward to meeting with Dominic Raab tomorrow.
“This is a vitally important meeting for the government and ourselves. We have not always been on the same page but it is more important now than ever that we are.”
On Sunday, Brexit Secretary Steve Barclay continued to assert the government’s position that they would not give up on getting Mrs Sacoolas extradited.
“We continue to work on that because we feel it is denying the family justice for her not to return to answer the questions that they have,” he told the BBC.
During a phone call with US president Donald Trump on Friday, the prime minister “reiterated the need” for Mrs Sacoolas to return to the UK, Downing Street said.