The United States is still working to determine how many Americans remain unaccounted for after Saturday's attack on Israel by Hamas and whether any are among those being held hostage in the neighboring Gaza Strip, according to National Security Council spokesman John Kirby.
In an interview Tuesday with ABC News' George Stephanopoulos on "Good Morning America," Kirby said the number of unaccounted Americans in Israel "keeps changing" as families contact the U.S. Department of State.
"We're trying to get a handle on where they are and how they are," he added. "Sadly, we have to accept the possibility -- the grim possibility -- that some of those unaccounted for Americans could be among those being held hostage by Hamas."
So far, U.S. officials have confirmed that at least 11 Americans were among those killed in Israel over the weekend when Hamas fighters stormed into the country from Gaza. U.S. officials are "preparing for the very distinct possibility that there'll be more" American deaths," Kirby said.
Meanwhile, there's currently no specific information on whether any Americans were among those taken hostage, according to Kirby. Israeli authorities have estimated that Hamas is currently holding "between 100 to 150" hostages in Gaza, including Americans.
"We're working at this really, really hard, talking to the Israelis every single day -- almost every hour -- to try to get more information about the Americans that are unaccounted for," Kirby said, "but we just don't know where they are."
U.S. officials have reached out to their Israeli counterparts to offer assistance in the form of intelligence and hostage recovery expertise, according to Kirby.
"It remains to be seen if there's Americans in that group, what more can be done," he said. "If there's Americans being held hostage, we'll do everything possible to get them home to their families where they belong."
When asked whether the U.S. would be prepared to pay ransom, Kirby said: "I don't want to get too far ahead of where we are."
"We don't even know if there are Americans in this population of hostages," he added.
Top US official talks Israel’s war with Hamas
National security council spokesman John Kirby discusses the United States’ concerns about the war in the Middle East and how the U.S. is offering support to Israel.