The pending Iranian strike, which could hit Israeli soil and target government or military buildings, has put both Israel and Washington on high alert.
Various reports have suggested an Iranian strike could be imminent and possibly as soon as this weekend.
White House national security spokesperson John Kirby said the threat from Iran is "viable" and the U.S. was working closely with Israel amid the impending action.
“We’re watching it very, very closely,” he said.
President Biden said the attack on Israel could happen soon and that the “expectation is sooner than later.”
“We are devoted to the defense of Israel,” he said. “We will support Israel and help defend Israel, and Iran will not succeed.”
The U.S. Embassy in Israel issued a security alert Thursday restricting American employees and their families from travel outside of the Tel Aviv area, Jerusalem and the southern city of Be’er Sheva.
The Iranian threat comes after an alleged Israeli strike earlier this month killed two top generals with Iran's Islamic Revolutionary Guard Corps.
The strike hit near the embassy in Damascus, Syria, and prompted an outcry in Iran, which views the attack on an official embassy as the same as a strike on Iranian soil.
Iran's Supreme Leader Ayatollah Ali Khamenei has repeatedly threatened to make Israel pay and has suggested that the country will be "slapped" for its strike.
ABC News reported that Iran is readying 100 cruise missiles for possible use in the attack.
Read the full report at TheHill.com.