WASHINGTON — Britain is close to identifying a man, thought to be British, who was shown beheading U.S. journalist James Foley in a video released by the Islamic State militant group last week, its ambassador to the United States, Peter Westmacott, told CNN.

“We are close” to identifying the man in the video, Westmacott told CNN’s “State of the Union” program on Sunday.

“We’re putting a lot into it,” he said, including using voice-recognition technology to track down the killer.

British authorities are trying to identify the man, who has a London accent and has been dubbed “Jihadi John” by British media. The masked figure beheaded Foley in a video released on Tuesday that also threatened a second captive American journalist, Steven Sotloff.

Foley was abducted in Syria in November 2012. Sotloff was kidnapped there in 2013.

Westmacott said the problem “goes beyond one horrendous criminal.”

“People think maybe as many as 500 British subjects have gone to Syria and Iraq for this cause of jihad,” he said.