Updated

Retired Marine Sgt. John "Tig" Tiegen, one of the four men who defended the Libyan consulate in Benghazi during the 2012 attack there, said the Iraqi government's slow response to a deadly attack on the U.S. embassy is a "slap in the face."

Tiegen told Charles Payne on Tuesday's "Your World" that, additionally, Iran must face retaliation -- as the attack appeared to be sanctioned by Tehran, according to the president.

"To me, this is a real big slap in the face on the Iraqis' [part] in my personal opinion," Tiegen told Payne.

"They allowed the protesters to walk through multiple security checkpoints before they got to the embassy," he continued, adding, "Something has got to happen against Iran. If they are backing it and Hezbollah is behind it, there has got to be some sort of retaliation against them."

Regarding the Iraqi government's purported "slap" to the U.S., Tiegen said it's the responsibility of the "host country" to protect embassies and consulates within their territories.

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He said that in the Baghdad case, it's unwise to have U.S. military forces firing upon civilians and protesters simply because they were setting fires and destroying property. He said it's Iraq's responsibility, in that case, to "protect American lives."

"If it comes down to it... make sure you shoot straight and shoot fast."

In addition, Tiegen expressed regret that, after the trillions of dollars spent in Iraq, incidents such as the embassy attack still have unfolded.

"This is what they do to us. It seems like there is a lot of backstabbing going on. They should have stopped the protests and should've had military people there when they saw the protests starting to move from the funeral," he said.

Earlier Tuesday, crowds of angry Iraqis protesting America’s recent airstrikes against an Iran-backed militia laid siege to the embassy compound, chanting "Down, Down USA!" as they stormed through a main gate, prompting U.S. guards to fire back tear gas in response.

As of Tuesday night, protesters set up tents outside the embassy in the Iraqi capital where they said they intended to stage a sit-in "until American troops leave Iraq and the embassy is closed." About 100 Marines were sent to the embassy to bolster security and an Army Apache helicopter flew over the premises and dropped flares in a "show of force," with the goal of dispersing the crowd, a U.S. defense official told Fox News.

Tiegen, a Colorado native, had helped defend the U.S. consulate in Benghazi, Libya, on Sept. 11, 2012, after it faced RPG and small arms fire.

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Militants killed U.S. Ambassador J. Christopher Stevens, as well as U.S. Foreign Service Officer Sean Smith and CIA contract protective officer Glen Doherty. Libyan militant Ahmed Abu Khattala later was sentenced to prison on terrorism-related charges in connection with the attack.

The Benghazi siege and U.S. response precipitated a high-profile congressional investigation, featuring testimony from then-Secretary of State Hillary Clinton.

Fox News' Eddie DeMarche and Greg Norman contributed to this report.