U.S. military commanders in the Middle East have drafted a slate of options to address possible security challenges facing Washington and allied efforts to disarm Syria.
Central Command submitted their recommendations to U.S. diplomats before Secretary of State John Kerry's meeting on Saturday with Russian counterparts to lay the groundwork for taking control of Syria's chemical weapons.
The command recommendations included "broad parameters ... to give us some idea of the dimensions of the security challenge" tied to taking control of Syria's chemical stockpiles, a State Department official said Sunday.
The official did not comment as to whether the command's recommendations included plans for U.S. forces to secure those sites.
President Obama has repeatedly insisted that no American troops will be deployed to Syria as part of potential U.S. operations in the country.
That said, "even in a regime-controlled area, we would need considerable security ... for protection of the site," the official said.
"If nothing else ... security is still a daunting challenge" to ensure Syria's chemical arsenal is fully accounted for, the official added.
Kerry and Russian Foreign Minister Sergey Lavrov agreed to a framework that will begin the handover of Assad's stockpiles to international control, led by the United Nations.
But recent reports claim Syrian military units are already hiding portions of Assad's chemical weapons in anticipation of U.N. inspections.
The Pentagon and White House remain adamant the deal will not require U.S. boots on the ground in Syria.
Keeping those weapon sites secure will be a job for the troops in Damascus, Pentagon officials insist.
"No matter what, [Syria] has an obligation" to account for its chemical weapons, Pentagon press secretary George Little said Friday.
The Assad regime "owes this [much] to the international community," Little said.
But on Thursday, Defense Intelligence Agency chief, Army Lt. Gen. Michael Flynn, said it could take as long as seven years to fully account for Syria's chemical weapons.
"I do not have a [high] level of confidence to get through this first iteration" of getting the weapons accounted for, under the Russia plan, according to Flynn.
"I'm hopeful that there's clear, cool-headed ... very long-view thinking and decision-making done," on how to secure the Syrian weapon sites, Flynn said.
"I'm not confident that it's going to happen overnight," the three-star general added.
On securing the chemical sites, the State Department official said Washington and Moscow were working with allied nations to address those concerns.
"The U.S. and Russia [are] committed ... to help find the resources with friends around the world," the official said, adding that several countries have already volunteered to assist with security.
"We have had previous discussions with a number of our allies and friends in Europe and elsewhere, particularly those who have technical capabilities in their military for dealing with [chemical weapons]," the official said.
In a July letter to Sens. Carl Levin (D-Mich) and John McCain (R-Ariz.), Chairman of the Joint Chiefs of Staff Martin Dempsey said "thousands" of U.S. ground troops would be needed to secure Syria's chemical weapon sites.
"Thousands of special operations forces and other ground forces would be needed to assault and secure critical sites" in the country, the four-star general said at the time.
Pentagon assessments in July reportedly estimated that 70,000 troops would be needed to lock down Assad's chemical weapons program, according to news reports at the time.