UK Prime Minister Boris Johnson urged the US on Monday to reconsider granting immunity to the wife of a US diplomat suspected of killing a teenager in a British road crash.

File photo: Xinhua

Johnson said he was prepared to intervene personally with the White House to ensure the woman's return to Britain, where she is a suspect in the death of 19-year-old ­Harry Dunn.

Dunn was killed on August 27 when his motorbike ­collided with a car near a Royal Air Force base in Northamptonshire, which is used by the US military as a communications hub.

He was hit by a Volvo SUV traveling in the opposite direction, according to police, who confirmed that a 42-year-old US woman being treated as a suspect in their investigations had left Britain.

The woman was not identified by name.

Johnson told reporters on a visit to a hospital, "I do not think that it can be right to use the process of diplomatic immunity for this type of purpose.

"I hope that Anne Sacoolas will come back and will engage properly with the processes of law as they are carried out in this country."

Foreign Secretary Dominic Raab has already raised the case with the US Ambassador to Britain, Woody Johnson.

"If we can't resolve it then of course I will be raising it myself personally with the White House," the prime minister added.

According to police, the woman said she had no plans to leave Britain in the near future.