The latest setback came in a remote area of Yemen early on Saturday, when al Qaeda militants shot American photo journalist Luke Somers and South African teacher Pierre Korkie during a rescue attempt led by U.S. Special Forces.
               
Defense Secretary Chuck Hagel defended the operation and the intelligence that lay behind it, and suggested there would be no wholesale review of U.S. policy.
               
"I don't think it's a matter of going back and having a review of our process. Our process is about as thorough as there can be. Is it imperfect? Yes. Is there risk? Yes," Hagel said on a visit to Tactical Base Gamberi in eastern Afghanistan.
               
"But we start with the fact that we have an American that's being held hostage and that American's life is in danger and that's where we start. And then we proceed from there," he said.
               
An earlier raid in mid-November to free Somers also was unsuccessful - he wasn't present when U.S. and Yemeni forces arrived - as was a July attempt to rescue American journalist James Foley, held by Islamic State in Syria. Foley was later beheaded.
               
Yet however high-risk, the increasingly frequent rescue attempts seem unlikely to stop now, particularly as Obama holds fast to a policy of refusing to pay ransom for captives.
               
A review of hostage policy that Obama ordered this summer will not include the issue of ransom, the White House has said.
               
That review was begun "in light of the increasing number of U.S. citizens taken hostage by terrorist groups overseas and the extraordinary nature of recent hostage cases," National Security Council spokesman Alistair Baskey said.
               
"Barack Obama's discovering what a nightmare dealing with hostage problems is - a discovery previously made by Jimmy Carter and Ronald Reagan," said Bruce Riedel, a former senior CIA and White House counter-terrorism official.
               
"I don't see a lot of room for change in American policy," said Riedel, now at the Brookings Institution think tank.
               
The Foley raid and the first attempt to free Somers failed because they apparently had been moved before U.S. Troops arrived, illustrating the limits of intelligence on captives' whereabouts. Somers and Korkie were shot by their captors when they detected the presence of the approaching Special Forces rescue team, officials said on Saturday.
               
The stepped-up rescue operations are a direct result of more than a decade of nearly non-stop raids against militants by elite U.S. forces in Iraq, Afghanistan and elsewhere.
               
"We're more capable now, borne out of 13 years of counter-terrorism," a senior U.S. defense official said. "But I wouldn't describe it as a more aggressive policy. ... the threat (to hostages), I think, is a little bit more pervasive too."
               
Sometimes the raids succeed. In January 2012, U.S. Navy SEALS parachuted into Somalia and rescued an American and a Danish aid worker, killing nine of their kidnappers.
               
"I think you have to try" to mount rescues, Riedel said. The message it sends, he said, is "one, we're not going to pay and two, the hostage-takers are at great risk."

Latest News from World News Desk