The United States will offer "every kind of support" to Israel when it comes to addressing the hostage situation in the Israel-Hamas war, a deputy national security adviser for the Biden administration told "CBS Mornings" on Monday.

"I expect the situation of the hostages to take on increasing focus over the course of the coming days," Jon Finer said, adding that the U.S. will be "laser focused" on confirmation of any Americans being held. 

"Just given the sheer numbers involved, we do expect that there may well be Americans who have been caught up in the hostage taking," Finer said. 

Hamas is believed to be holding scores of hostages after hundreds of members of the militant group, which has long been designated a terrorist organization by the U.S. and Israel, launched their assault on Saturday. Some Hamas fighters smashed through a barrier that Israel has used for decades to contain Palestinians inside the Gaza Strip, while others infiltrated Israel by air and sea. 

Gunmen from the group slaughtered civilians in the streets and kidnapped people — including women, children and the elderly — who were believed to be transported into Gaza. Israel's Government Press Office said on Sunday that Hamas took more than 100 people hostage.

The U.S. was working to verify reports that Americans were among those taken, Secretary of State Antony Blinken said Sunday.

"We've got reports that several Americans are among the dead. We're working very actively to verify those reports. At the same time, the reports of Americans being taken hostage — there too, we're working to get the facts to find out if those reports are accurate," Blinken said on "Face the Nation."  

Officials said more than 700 Israelis have been killed, mostly civilians, including more than 250 who had been attending a music festival near the border with Gaza when the attack took place. At least nine Americans are among the dead, a U.S. National Security Council spokesperson confirmed Monday. An undetermined number remained missing.

Hundreds of Palestinians have been killed in Israel's response to Hamas' assault.

Hamas, which runs the Gaza Strip, is backed by Iran. But Finer said that while Iran is "broadly complicit in these attacks" and has been Hamas' "primary backer for decades," the U.S. has not seen "any sort of direct involvement in the immediate attacks that took place over the last couple of days."

"The Israel Defense Forces are saying the same thing: broad complicity for Iran, no sign of any immediate direction," he said, "although this is obviously something that we are going to continue to watch very closely."

Republican presidential candidates are trying to link Hamas' assault to the recent U.S. deal with Iran that brought five American prisoners home and included unfreezing $6 billion in Iranian oil assets. The White House has sharply pushed back, insisting that the money is safeguarded for food and humanitarian aid, and that not a single cent of that money has been spent — let alone to fund terrorists. 

CBS News' Haley Ott, Holly Williams, Weijia Jiang and Caitlin Yilek contributed to this report.   

In:
• Israel
• Gaza Strip