James Foley’s killers wanted a $132 million ransom for his release, his employer has said.
GlobalPost CEO Philip Balboni said the Islamic State (ISIS) militants first demanded money last year.
James Foley was abducted in November 2012, and a video of his beheading was released by ISIS earlier this week.
In the video, they threatened to kill another American, journalist Steven Joel Sotloff, if the US did not stop its air strikes against the group in northern Iraq.
US air strikes have continued near Mosul despite the warning.
The US has begun a formal criminal investigation into James Foley’s death, with Attorney General Eric Holder saying that the US has a “long memory and our reach is very wide”.
In the UK, police and security services are trying to identify the jihadistwho appeared in footage of James Foley’s killing.
Unconfirmed reports suggest the man – who had a British accent – is from London or south-east England.
On Thursday, Eric Holder said the US pursuit of James Foley’s killer would be determined.
“We have an open criminal investigation, and those who would perpetrate such acts need to understand something: this Justice Department, the Department of Defense, this nation, we have long memories and our reach is very wide,” he said.
“We will not forget what happened and people will be held accountable one way or the other.”
Earlier President Barack Obama condemned the killing and vowed to bring the perpetrators to justice.
“We will be vigilant and we will be relentless,” he said.
“When people harm Americans, anywhere, we do what’s necessary to see that justice is done.”
The US launched more air strikes on ISIS targets in Iraq on Thursday.
US aircraft destroyed or damaged four ISIS vehicles and several bomb placements in strikes near Mosul dam, the military said.
Since August 8, the US military says it has conducted a total of 90 airstrikes across Iraq.
Of those 90 strikes, 57 have been near Mosul Dam, the military said.
The US defense department has revealed that the US “attempted a rescue operation recently to free a number of American hostages held in Syria”.
“Unfortunately, the mission was not successful because the hostages were not present at the targeted location.”
It was the first time the US government had acknowledged that its forces had operated in Syria since the country’s civil war began in 2011.
The Pentagon statement did not specify whether the operation had intended to rescue James Foley.
However, senior US officials – speaking on condition of anonymity – confirmed this. They added that the troops had killed several ISIS militants.
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