"We understand the dynamics" within the rebel forces in Syria, including infiltration by militant groups like Jabhat al-Nusra (JAN) and al Qaeda in Iraq (AQI) into the opposition, according to Pentagon Press Secretary George Little
Concerns over that growing influence within Syria's rebels over the two-year civil war to overthrow president Bashar Assad have been the major roadblock in possible U.S.-led efforts to provide small arms and heavy weaponry to anti-Assad forces.
Military and intelligence officials those U.S. weapons, if provided, could end up in the hands of al Qaeda fighters.
The merger between AQI and JAN earlier this month was thought to have extinguished any possibility for American weapons being sent to Syria, since the deal quelled any doubt that al Qaeda has secured a foothold in the country.
But President Obama opened the door to arming the rebels on Tuesday, over concern the Assad regime may be using chemical weapons against opposition forces.
While Obama has yet to make a final decision on supplying arms to opposition forces, a decision could be made in the coming weeks -- before a June meeting with Russian President Vladimir Putin, who has backed the Syrian regime.
Washington and its regional allies in the Mideast are making a concerted effort to reach out to "a large number" of moderate groups within the opposition "that want a political solution" for Syria once president Bashar Assad falls, Little said.
"This is not just about chemical weapons. This is not just about extremist groups" in Syria, he said.
Little declined to comment on whether the White House has requested recommendations on military options for Syria from the Department of Defense, including arming the country's rebels.
He also declined to comment on whether the Obama administration has set a deadline for the DOD to provide assessments on possible military action in the country.
"There are meetings that are taking place" at the White House with Pentagon leaders, as well as other U.S. officials from the State Department and intelligence community, Little said.
That said, Pentagon leaders have been drafting possible military options for Syria since the conflict erupted in late 2011, according to Little.
"That is our responsibility," he said regarding the department's planning. "We believe it is important to have options on the shelf."
As part of that planning, American military leaders are looking at options for "the day after" Assad falls, Little said.
Those post-Assad plans are "something that we are considering" as Washington continues to reach out to allies in Turkey, Jordan and other countries in the region.
DOD leaders have already sent an Army headquarters unit to Amman last week to help the country's military defend its shared border with Syria.
That unit, along with U.S. military trainers already in Jordan, will provide "training and equipment" to prevent any Syrian chemical weapons from being smuggled into the country.
Earlier this year, Washington deployed a battery of American Patriot anti-missile weapon systems along the Turkish-Syria border.
Sens. Carl LevinCarl LevinSenate about to enter 'nuclear option' death spiral Devin Nunes has jeopardized the oversight role of Congress Ted Cruz wants to destroy the Senate as we know it MORE (D-Mich.), John McCainJohn McCainOvernight Finance: Senate Dems call for investigation of acting SEC chairman | Wyden: Russia probe should focus on Trump financial ties | Dems seek more money for IRS Overnight Defense: Pentagon considers more troops for Afghanistan | McCain, Graham won't back short-term funding | GOP defends Trump rules of engagement McCain and Graham: We won't back short-term government funding bill MORE (R-Ariz) and Lindsey GrahamLindsey GrahamOvernight Finance: Senate Dems call for investigation of acting SEC chairman | Wyden: Russia probe should focus on Trump financial ties | Dems seek more money for IRS Overnight Defense: Pentagon considers more troops for Afghanistan | McCain, Graham won't back short-term funding | GOP defends Trump rules of engagement McCain and Graham: We won't back short-term government funding bill MORE (R-S.C.), are calling for U.S. arms to be sent to Syria.
They have also called for the deployments of American warplanes into Syria to take out Assad's heavy weapons and the creation of a no-fly zone along the country's border with Turkey.