U.S. intelligence shows that Iranian officials were surprised by Palestinian militant group Hamas' terror attack Saturday on Israel, CBS News reported.

Citing multiple unidentified American officials, CBS reported Wednesday that preliminary assessments indicate that Iranian officials who would usually be aware of such operations in the region seemed to have no knowledge that an attack was occurring.

CBS' sources would not elaborate on the Iranian officials' identities or on the type of intelligence that was gathered.

"[W]e have said since the beginning that Iran is complicit in this attack in a broad sense because they have provided the lion's share of the funding for the military wing of Hamas, they have provided training, they have provided capabilities, they have provided support, and they have had engagement and contact with Hamas over years and years," national security adviser Jake Sullivan told reporters on Tuesday.

"We'll be looking at additional intelligence in the coming weeks and days to inform our thinking on this issue, including whether at least there were some in the Iranian system who either had a clear sense of what was coming or even contributed to aspects of the planning," State Department spokesman Matthew Miller said during a Tuesday press briefing.

Congressional lawmakers on Wednesday received a classified briefing by multiple agencies on the situation in Israel and Iran's possible role in the attack, according to CBS. A smaller group of lawmakers was also reportedly briefed by senior U.S. intelligence official Morgan Muir on Tuesday.

Biden administration officials have said that Iran has been a longtime provider of material, financial, and logistical support to Hamas, but have maintained that no evidence has been found to link Tehran directly to the attack.

Secretary of State Antony Blinken told CNN's "State of the Union" on Sunday that "no U.S. taxpayer dollars were involved" in the massacre — pushing back on suggestions that the Biden administration's deal to release $6 billion in frozen Iranian assets last month helped fund the operation.

"These were Iranian resources that Iran had accumulated from the sale of its oil that were stuck in a bank in South Korea," Blinken said. "They have had from day one, under our law, under our sanctions, the right to use these monies for humanitarian purposes — from one account to another in another country to facilitate that use. As of now, not a single dollar has been spent from that account."

Blinken traveled to Israel on Wednesday in an attempt to contain the Gaza Strip hostilities from flaring up into a wider conflict.

"I'm going with a very simple and clear message ... that the United States has Israel's back," Blinken told reporters.

According to published reports, approximately 1,100 Israelis were killed in the attack, with hundreds more wounded and dozens taken hostage by Hamas.

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