Washington (CNN) - President Barack Obama called the widow of Sean Smith the day following the attack on the U.S. mission in Benghazi, Libya, promising to "avenge" the deaths of her husband and the three other Americans killed, according to a new book by reporter Michael Hastings.
Communications specialist Smith was among four killed in an attack on a diplomatic post in Benghazi, Libya on September 11, 2012, including U.S. Ambassador Christopher Stevens.
Obama spoke with Heather Smith on September 12th as he flew to a campaign rally in Las Vegas on Air Force One. The White House confirms to CNN the call took place and notes the president said similar things about avenging the deaths of the four murdered Americans publicly in his statements following the attack.
"We will not waver in our commitment to see that justice is done for this terrible act," Obama said at that campaign rally. "And make no mistake, justice will be done."
"Obama told her he was going to avenge the deaths of Sean and the others. He offered her his condolences," Hastings writes in his book 'Panic 2012.'
"I don't feel like he said the wrong things," Heather Smith said, according to Hastings.
Hastings reports that Secretary of State Hillary Clinton also called Heather Smith that day.
The information comes as Clinton provides testimony to the U.S. Senate and House Foreign Relations Committees Wednesday about the State Department's handling of the attack. She told the Senate Foreign Affairs committee that there were "very promising leads" and cases were being put together.
The investigation into the Benghazi killings continues and has made "significant progress," a law enforcement official told CNN Justice Producer Carol Cratty last week. The official suggested charges were expected but did not provide a timetable. FBI Director Robert Mueller traveled to Tripoli last week to meet with Libyan officials.
The U.S. is focused on "more than a dozen people," another U.S. official told CNN's Susan Candiotti recently. But one suspect, a Tunisian named Ali Harzi, has been the source of frustration for the U.S. investigators. Harzi was arrested in Tunisia but was recently released.
Clinton told the Senate Foreign Affairs committee she has been assured by the Tunisian government that Harzi is being monitored.
"Upon his release, I called the Tunisian prime minister. A few days later Director Mueller met with the Tunisian prime minister. We have been assured that he is under the monitoring of the court. He was released, because at that time - and Director Mueller and I spoke about this at some length - there was not an ability for evidence to be presented yet that was capable of being presented in an open court," Clinton said Wednesday.
Clinton said the president will hold true to his word that justice will be served.
"I don't think anybody should doubt this president at his word," Clinton told the committee. "We have some very good examples of that. It may take time, but he does not in any way divert attention from the goal of bringing them to justice."