The U.S. and its allies are working to free a 26-year-old American aid worker kidnapped by the Islamic State group in 2013, U.S. President Barack Obama said in an NBC interview to be aired on Monday. The militant group Saturday released a video purportedly showing a militant beheading Japanese journalist Kenji Goto.  

Obama called her capture “heartbreaking” and said he watched the Islamic State group’s beheading videos, the Associated Press reported. The radical group’s practices affirm his administration’s decision to undertake airstrikes against the group in Iraq and Syria, he said. The woman is the fourth American to be taken hostage by the Islamic State group.

The administration has kept a tight lid on the identity of the woman and asked media outlets to refrain from using her name out of concern for her safety although White House chief of staff Denis McDonough accidentally said her first name in an interview with ABC News last week. Her exact location is unknown. McDonough said in the interview the government was “sparing no expense, and sparing no effort, both in trying to make sure that we know where they are and make sure that we’re prepared to do anything we must to get them home.”

All three of the other Americans who had been taken hostage were beheaded on camera last year. Veteran journalist James Foley captured in 2012 was the first of the three to be beheaded in August of last year. Another journalist, Steven Sotloff was kidnapped in 2013 and beheaded in September while Peter Kassig, an aid worker and former Army ranger who was captured in late 2013 was killed in November. The Islamic State group demanded the U.S. stop its air campaign against the extremists in exchange for the hostages’ lives.