"The United States attempted a rescue operation recently to free a number of American hostages held in Syria by the Islamic State of Iraq and the Levant (IS)," Pentagon spokesman Rear Admiral John Kirby said in a statement.
"This operation involved air and ground components and was focused on a particular captor network within ISIL (IS).
"Unfortunately, the mission was not successful because the hostages were not present at the targeted location."
The White House said in a separate statement that the rescue attempt was authorized "earlier this summer."
American reporter James Foley was kidnapped in northern Syria in November 2012.
The video of his execution, released Tuesday, also showed a second US reporter, Steven Sotloff, being paraded on screen.
It was not immediately clear if either reporter was the target of the failed US rescue mission.
IS, also known as ISIL, considers Washington its arch enemy and has overrun large swaths of Iraq and Syria.
It says it represents the aspirations of a global Muslim caliphate.
"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," said Kirby.
"In this case, we put the best of the United States military in harms' way to try and bring our citizens home."
In a White House statement on the rescue attempt, Lisa Monaco, assistant to President Barack Obama for Homeland Security and Counterterrorism, said: "The president 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.
"The US 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.
IS 'masters of social media', says Abbott
Prime Minister Tony Abbott has described the Islamic State as perhaps the most effective terrorist organisation the world has seen.
The prime minister was speaking again about the shocking new video of an IS jihadist beheading American journalist James Foley, who was captured in Syria in 2012.
Mr Abbott was asked whether the British accent of the executioner was intended as a message to the West about the role of foreign fighters in the conflict.
"I have little doubt that the ISIL movement are masters of propaganda. They're masters of social media," Mr Abbott told Fairfax Radio in Melbourne.
"They are probably the most effective terrorist organisation the world has yet seen. That's why it's very important we redouble our vigilance."
Mr Abbott said the 60 or so Australians fighting with IS - also known as ISIL and ISIS - represented only a "miniscule" percentage of the country's population.
But he warned it did not take many people "to do enormous damage to countries".
Mr Abbott is adamant Australia and other Western nations will not commit combat troops to battle IS in northern Iraq.
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