WASHINGTON (AP) — President Barack Obama sent special operations troops to Syria this summer on a secret mission to rescue American hostages, including journalist James Foley, held by Islamic State extremists, but they did not find them, the Obama administration said Wednesday.

Officials said the rescue mission was authorized after intelligence agencies believed they had identified the location inside Syria where the hostages were being held. But the several dozen special operations forces dropped by aircraft into Syria did not find them at that location and engaged in a firefight with Islamic State militants before departing, killing several militants. No Americans died but one sustained a minor injury when an aircraft was hit.

"The U.S. government had what we believed was sufficient intelligence, and when the opportunity presented itself, the president authorized the Department of Defense to move aggressively to recover our citizens," said Lisa Monaco, Obama's top counterterrorism adviser, in a statement. "Unfortunately, that mission was ultimately not successful because the hostages were not present."

Officials disclosed the rescue operation a day after the militants released a video showing the beheading of Foley and threatened to kill a second hostage, Steven Sotloff, if U.S. airstrikes against the militants in Iraq continued.

Despite the militants' threats, the U.S. launched a new barrage of airstrikes against Islamic State targets in Syria Wednesday. The Obama administration did not rule out the prospect of a military operation in Syria to bring those responsible for Foley's death to justice.

The disclosure of the rescue mission marks the first time the U.S. has revealed that American military personnel have been on the ground in Syria since a bloody civil war there broke out more than three years ago. Obama has resisted calls to insert the U.S. military in the middle of Syria's war, a cautious approach his critics say has allowed the Islamic State to strengthen there and make gains across the border in Iraq.

"As we have said repeatedly, the United States government is 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," Pentagon spokesman Rear Adm. John Kirby said in a statement Wednesday night. "The United States government uses the full breadth of our military, intelligence and diplomatic capabilities to bring people home whenever we can. The United States 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."

It's unclear how many Americans the special forces attempted to rescue in Syria. While the officials who described the mission would not provide an exact number, other U.S. officials, who were not authorized to speak publicly, have said Foley was one of at least four Americans held in Syria.

Like Foley, two others are believed to have been kidnapped by the Islamic State. The fourth, freelance journalist Austin Tice, disappeared in Syria in August 2012 and is believed to be in the custody of government forces in Syria.

Administration officials would not say specifically when or where the operation took place, citing the need to protect operational details in order to preserve the ability to carry out future rescue missions. They did say that nearly every branch of the military was involved and that the special forces on the ground were supported from the air by fixed wing, rotary and surveillance aircraft.

Obama has authorized previous military missions to rescue hostages. In 2009, Navy SEAL snipers carried out a daring sea operation to rescue an American ship captain held by Somali pirates in a lifeboat. And in 2012, special operations forces successfully rescued an American and Dutch aid worked held in Somalia.

Read Monaco's full statement below: