He says ISIS have "rampaged" across towns and villages in Iraq and Syria, committing "cowardly acts of violence" in the name of a "bankrupt" ideology that is of no value to human beings in the 21st century.
"People like this fail," he said. "The world is shaped by those like Jim Foley... and those who are appalled by those who killed him."
He said the world must "extract this cancer so it does not spread", adding: "We will do everything we can to protect our people."
"We will continue to confront this hateful terrorism and replace it with a sense of hope and stability.
"That's what Jim Foley stood for. A man who lived his work, who courageously told the stories of his fellow human beings and who was liked and loved by friends and family."
Mr Foley's family also spoke movingly this afternoon about the reporter, with dad Jon speaking of his pride in his son.
He told reporters: "Jimmy's free and we know he's in God's hands and we know he's in heaven. We're so proud of him."