The United States will not pay ransoms for those Americans, who are being held hostage overseas, despite U.S. President Barack Obama's request to review the U.S. response to such situations, White House spokesperson said.

"The reason we [the United States] are not reviewing the policy as it relates to not paying ransom is that our views on this are clear… we don't want to put other American citizens at an even risk when they are around the globe," Josh Earnest said at a press briefing on Tuesday, Nov 18, according to Sputnik.

"Based on our insight into the way that ISIL works… they rely on these sort of ransom payments as a very important source of their financing," Earnest said. "So shutting off that [ransom payments] source of financing is an important part of our strategy for defeating them."

Earnest added that the US Department of Defense, the Department of State, Federal Bureau of Investigation (FBI) and other members of the intelligence community have been reviewing the U.S. hostage response efforts, but would not say when the review would be concluded.

On Sunday, American aid worker Peter Kassig was executed by IS fighters after he was captured by the group in Eastern Syria in October 2013.