The official position is that the US has refused to allow heavy weapons into Syria.
But there's growing evidence that U.S. agents—particularly murdered ambassador Chris Stevens—were at least aware of heavy weapons moving from Libya to jihadist Syrian rebels.
In March 2011 Stevens became the official U.S. liaison to the al-Qaeda-linked Libyan opposition, working directly with Abdelhakim Belhadj of the Libyan Islamic Fighting Group—a group that has now disbanded, with some fighters reportedly participating in the attack that took Stevens' life.
In November 2011 The Telegraph reported that Belhadj, acting as head of the Tripoli Military Council, "met with Free Syrian Army [FSA] leaders in Istanbul and on the border with Turkey" in an effort by the new Libyan government to provide money and weapons to the growing insurgency in Syria.
Last month The Times of London reported that a Libyan ship "carrying the largest consignment of weapons for Syria … has docked in Turkey." The shipment reportedly weighed 400 tons and included SA-7 surface-to-air anti-craft missiles and rocket-propelled grenades.
Those heavy weapons are most likely from Muammar Gaddafi's stock of about 20,000 portable heat-seeking missiles—the bulk of them SA-7s—that the Libyan leader obtained from the former Eastern bloc. Reuters reports that Syrian rebels have been using those heavy weapons to shoot down Syrian helicopters and fighter jets.
The ship's captain was "a Libyan from Benghazi and the head of an organization called the Libyan National Council for Relief and Support," which was presumably established by the new government.
That means that Ambassador Stevens had only one person—Belhadj—between himself and the Benghazi man who brought heavy weapons to Syria.