The Obama administration's senior counterterrorism official acknowledged Thursday that U.S. intelligence was surprised by the collapse of the U.S.-backed government in Yemen.

Nick Rasmussen, who directs the National Counterterrorism Center, told the Senate intelligence committee that Yemen's American-funded army failed to oppose advancing Houthi rebels in the same way the U.S.-supported Iraqi military refused to fight Islamic State militants last year.

What happened in Iraq with the onslaught of the Islamic State group "happened in Yemen" on "a somewhat smaller scale," he said. "As the Houthi advances toward Sanaa took place ... they weren't opposed in many places. ...The situation deteriorated far more rapidly than we expected."

Rasmussen made the admission under questioning by Sen. Roy Blunt, a Missouri Republican who noted that President Barack Obama recently touted Yemen as a success. Now, it's a "total disaster," Blunt said.

In response to other questioning, Rasmussen also noted that extremists in Libya, Afghanistan, Egypt and Algeria had pledged allegiance to the Islamic State group, suggesting a growing influence of that al-Qaida rival.

The Islamic State group is now the dominant extremist group in the Libyan cities of Derna and Benghazi, where a 2012 attack killed four Americans including U.S. Ambassador Chris Stevens.

"We've seen in recent months ISIL has looked to expand its reach in a number of places," Rasmussen said.

He acknowledged that efforts against al-Qaida's Yemen affiliate, considered one of the most dangerous to Americans, had been significantly diminished by the collapse of the government and this week's evacuation of the U.S. Embassy.