President Joe Biden said on Monday that at least 11 American citizens were among those killed in Israel following this weekend's attacks by Palestinian Islamist group Hamas.
Earlier in the day, the U.S. had confirmed nine dead.
He also said some Americans are likely among hostages being held by Hamas, which has threatened to execute captives over potential Israeli retaliation in Gaza.
"While we are still working to confirm, we believe it is likely that American citizens may be among those being held by Hamas," Biden said.