"It would be an act of gross negligence if we did not take the necessary precautions in the light of credible threat streams," said one of the unnamed officials who briefed reporters on Wednesday, on the department's condition of anonymity. "That does not mean we are rushing to a conflict."
Early Wednesday, the State Department announced it was withdrawing all non-essential personnel from the U.S. Embassy in Baghdad and the U.S. consulate in Erbil "given the current security conditions," but did not detail the nature of any threat.
The senior State Department officials said the decision was made because of "increased intelligence reporting" that came to light after Secretary of State Mike Pompeo made a surprise visit to Baghdad last week. However, the officials characterized the threat as not more credible or imminent than it was in the week prior, as the U.S. moved military assets to the region and warned of Iranian-related threats.
U.S. officials told ABC News last week that there were "clear indications" Iran or its proxy forces were preparing for a possible attack against U.S. forces at sea and on land, including in Iraq and Syria, prompting the deployment of a carrier strike group and bomber task force to the region.
"I would urge the State Department and DOD to come down here and explain to us what's going on because I have no idea what the threat stream is beyond what I read in the paper," said Sen. Lindsey Graham, R-S.C., on Wednesday.
Sen. Bob Menendez, D-N.J., expressed similar frustration that lawmakers had not been briefed by the administration.
"There are only two reasons for ordering their departure: We have credible intelligence that our people are at risk or in preparation for military action in Iran. The Trump administration has not provided any information to this committee on the intelligence behind their decisions or what they plan to do in Iraq or Iran, and I have repeatedly reminded the administration of its responsibilities to this committee," Menendez said.
"What we have heard so far has been shallow and superficial at best," Rep. Tulsi Gabbard, D-Hawaii, told ABC's Senior Washington Reporter Devin Dwyer on ABC News Live.
The presidential candidate and Iraq war veteran added, "What we're seeing instead are actions coming from President Trump and his administration, led by John Bolton, that are dangerously escalating us closer and closer toward a devastating war with Iran."
Some Trump administration critics, including Gabbard, have drawn comparisons to how the Bush administration used intelligence to gain support for invading Iraq in 2003, a comparison senior State Department officials squarely dismissed.
"I went through this same thing in Iraq, a war that was championed by people like John Bolton who lied to us and the American people saying, 'Saddam Hussein has weapons of mass destruction; he's going to give them to al-Qaeda' -- evidence that turned out to be false," Gabbard said.
"Comparisons to Iraq 2003 are simply wrong," said senior State Department officials. "The much more appropriate analogy is Iraq 2011."
"This threat stream is very similar to what we saw in 2011 in Iraq, where they were firing the equivalent of barrel bombs at our installations," the officials said later, adding "and it's the same [Iranian-backed Iraqi] groups: it's Asaib Ahl al-Haq, it's Kataib Hezbollah, it's [Islamic Revolutionary Guard Corps]-commanded and controlled Iraqi militias, and so I'm seeing the same threat reporting and I'm seeing the same preparations that I saw back then."
But while non-essential U.S. personnel depart Iraq, over 5,000 service members remain in the country. U.S. Central Command acknowledged on Tuesday that those troops are operating at an increased posture level, adding that the U.S.-led coalition was "now at a high level of alert" as it continued to monitor threats against U.S. forces.
That "high level of alert" affects how U.S. troops operate, limiting the movement of non-essential service members and requiring them to bring full equipment "everywhere they go for protection and security," a U.S. official said on Wednesday.
This is far from the first time the U.S. has made changes to its diplomatic posture in Iraq. In September, the U.S. ordered the evacuation of its consulate in Basra -- Iraq's second largest city -- because of attacks that the U.S. said were perpetrated by Iranian-backed militias. Those rockets landed just outside the airport compound where the U.S. consulate was located, but did not kill or injure anyone.