"I think our efforts to get Jim freed were an annoyance" to U.S. officials, Diane Foley told CNN's Anderson Cooper.
Messages of grief and solidarity have poured in from around the globe to remember the life of James Foley, the American journalist beheaded by ISIS.
American hostages were treated more harshly than European prisoners and Foley was repeatedly tortured, sources said.
Syria said that it would welcome the cooperation of the United States in fighting ISIS.
British intelligence officials have identified the man they believe killed American journalist James Foley in Syria, sources told NBC News on Sunday.
"All letters Jim wrote to his family during his captivity were confiscated by the jailers. So, Jim devised a better approach this last June."
James Foley will be remembered Sunday at a Mass of Remembrance in his hometown of Rochester, New Hampshire.
Iraqi President Fuad Masum also used the letter to call attention to “boosting the freedom of journalists.”
“When you see somebody killed in such a horrific way, that represents a terrorist attack,” a White House official said.
The last time James Foley's parents heard from their son's captors was on Aug. 12. They received this message.
Britain’s role as a source of jihadis is under the spotlight after the beheading of American James Foley - likely by an ISIS fighter from the U.K.
Three Islamist militants with British accents have been dubbed "The Beatles" by hostages taken in Syria.
The U.S. killed several ISIS fighters during their mission to rescue James Foley and other hostages in early July, U.S. officials said.
Pope Francis called the family of James Foley, a Vatican spokesperson said
The U.S. tried and failed to rescue Foley in 2012.
James Foley, who traveled to Earth's most dangerous corners, "didn't let fear hold him back," his best friend said — but added he was never reckless.
Twitter banned users sharing graphic images of deceased journalist James Foley. Did it make the right call?
The U.S. tried to rescue James Foley and other hostages held in Syria by Islamist militants, but the mission failed because the hostages weren't there, officials said.
Foley, a 40-year-old American journalist held in Syria since 2012, was beheaded by militants from the Islamic State of Iraq and al-Sham, or ISIS.
Although he was killed by ISIS, Jim's quest to chronicle modern war lives on through his journalism. Here's a sampling of his work for GlobalPost.
Dimitri Bontinck says only two percent of those who left home to fight in Syrian can be persuaded to return to their home countries.
The journalist's mother and father said they did not watch the video of his beheading but are "haunted" by his cruel death.
Colleagues and loved ones remembered the slain American war correspondent as dedicated to his profession and friends.
The president planned to speak after the militant group ISIS beheaded an American journalist.
Steven Joel Sotloff, 31, grew up in Miami and attended the University of Central Florida.
Counterterrorism police in the U.K. warned it may be an offense to watch a video purportedly showing American journalist James Foley being beheaded.
James Foley said seeing "something really violent, it does a strange thing to you."
Foley was kidnapped at gunpoint near the town of Taftanaz in northern Syria on Thanksgiving Day in 2012.