He stated this on the third day since Palestinian militants launched a stunning and complex surprise attack in Israel.
In a statement, Biden described the deaths as the “heart-wrenching” results of an “appalling terrorist assault against Israel.”
He said the U.S. believed that the Hamas militant group was likely holding American citizens as prisoners.
He added that the U.S. is working with Israel to handle the hostage crisis.
“This is not some distant tragedy,” the President said in his statement.
“The ties between Israel and the United States run deep. It is personal for so many American families who are feeling the pain of this attack,” the President added.
The identities of the dead Americans were not immediately released, and it was unclear if any were from New York, which is home to about 1.6 million Jews.
In New York City, there was a heavy police presence at synagogues on Monday.
Major U.S. airlines have canceled flights into and out of Israel.
At least 50 New York residents were seeking to return from Israel on Monday, according to a count by Rep. Grace Meng’s office.
The State Department said it was in contact with the families of the dead Americans.
More than 1,300 people have already been reported dead in the conflict, which was escalating Monday as Israel ordered an intense retaliatory assault on the blockaded Gaza Strip.
At least 700 people have died in Israel, according to the Israel Defense Forces.
The Palestinian death toll was 687, the Palestinian Health Ministry said Monday.
