US reveals summer operation in Syria to free American hostages failed

The US had staged an unsuccessful operation this summer to rescue American hostages held in Syria by the militant group ISIL, the Pentagon has said.

The disclosure came a day after ISIL released a disturbing video showing a member of the extremist group beheading Foley.

"This operation involved air and ground components and was focused on a particular captor network within ISIL. Unfortunately, the mission was not successful because the hostages were not present at the targeted location," Pentagon Press Secretary John Kirby said.

Earlier this summer, President Barack Obama had authorized an operation to attempt the rescue of Americans who were kidnapped by the ISIL and held in Syria, said Lisa Monaco, Assistant to President for Homeland Security and Counter -terrorism.

Obama authorized action at this time because it was the national security team's assessment that these hostages were in danger with each passing day in ISIL custody, she said.

Monaco said the US Government had what it believed was sufficient intelligence, and when the opportunity presented itself, the President authorized the Department of Defense to move aggressively to rescue the hostages.

"Unfortunately, that mission was ultimately not successful because the hostages were not present," she said, adding "given the need to protect our military's operational capabilities, we will not be able to reveal the details of this operation."

Meanwhile Kirby said that the US was committed to the safety and well-being of its citizens, particularly those suffering in captivity.

"In this case, we put the best of the United States military in harms' way to try and bring our citizens home," he said.

"The US government uses the full breadth of our military, intelligence and diplomatic capabilities to bring people home whenever we can. America will not tolerate the abduction of our people, and will work tirelessly to secure the safety of our citizens and to hold their captors accountable," the Pentagon spokesperson said.