Still image from undated video of a masked Islamic State militant holding a knife speaking next to man purported to be James Foley at an unknown location
A masked Islamic State militant holding a knife speaks next to man purported to be U.S. journalist James Foley at an unknown location in this still file image from an undated video posted on a social media website. Britain is close to identifying a suspected British national shown beheading American journalist James Foley in a video released by Islamic State militants last week, the British ambassador to the United States said on August 24, 2014. Reuters/Social Media Website

U.S. authorities working to identify the man behind the black-masked Jihadi John, executioner of American journalist James Foley, said they hope to release his true identity to the world within days before he gets killed out on the battlefield.

Authorities from both the U.S. and the United Kingdom want executioner Jihadi John alive as much as possible.

CNN, citing two unidentified U.S. officials, reported the identity of Foley's executioner has been pretty much established, although "it's not 100 per cent yet."

The officials said they have been using all means to identify the person, including voice analysis and analyzing metadata from the video as well as other methods, so "we have a pretty good idea of who it may be."

The UK has interests in the ongoing investigation because black-masked Jihadi John is believed to be a British citizen who traveled overseas to join the IS cause.

Authorities believed the man is in Syria and still alive.

"This person is in an environment that's highly dangerous. He could meet his demise on the battlefield," the official said.

Earlier this week, British MI5 said that Jihadi John was part of a list of people that the agency tracked before he left for the Middle East as a collector for Arab charities.

It was reported that he gathered funds for the Islamic state after finishing work with the genuine charities.

"Like so many jihadists before him, he then seems to have become radicalised almost overnight and disappeared to travel to the Middle East," an unidentified source told The Mirror.

Jihadi John is believed to be one of four jihadists from the U.K., known as the "Beatles." Foley and another recently beheaded American journalist Steven Sotloff were not the first hostages they had executed in Syria.

American and British authorities said they have also identified who the other three jihadis were.

Authorities are currently pressed to save the life of British aid worker David Haines, who according to the masked jihadi that executed Sotloff said is next for execution.

Meantime, counter-terrorism authorities in UK have been reported to be arresting soon up to a dozen suspected British associates of hostage killer Jihadi John.

The Daily Record said the 12 people were the ones who "provided money, contacts and facilitated travel to Syria" to Jihadi John.