BEIRUT, Lebanon - Heavy antitank missiles recently shown in videos being fired by Western-backed Syrian rebels were manufactured in the United States, and their transfer to the rebels would have required direct U.S. government approval, according to experts in international weapons deals.

That makes the videos the first hard evidence that the Obama administration has undertaken what may be a test of the rebels' ability to adapt to advanced arms.

The videos, posted on the Internet over the last three weeks by the Harakat Hazem rebel group, affiliated with the U.S.-backed Supreme Military Council, show rebels firing BGM-71 TOW missiles, a wire-guided antitank weapons system capable of piercing the armor on the Syrian military's heaviest battle tank.

Only three videos have been posted so far, suggesting that the number of missiles provided has been relatively few and that the availability of more missiles may depend on the rebels' ability to use them and their success at documenting that they haven't fallen into the hands of al-Qaeda-affiliated groups.

State Dept. reaction

"I was aware that the decision had been made to send better equipment through the Saudis but did not know they had arrived on the ground until the videos appeared," said a Beirut-based Western military attaché, who spoke only on the condition of anonymity because of security concerns.

The State Department declined to confirm that the administration has agreed to the missile delivery. A State Department official, speaking only on the condition of anonymity, confirmed only that the United States was trying to improve the training of and weaponry available to rebel groups that the U.S. thinks are free of al-Qaeda influence.

As the Syrian rebel movement has grown increasingly Islamist in nature - four of the largest, most effective groups have ties to al-Qaeda - early American promises of military training and equipment have failed to materialize because of fears that advanced weapons and training could end up in the hands of past and future American adversaries.

Saudi link

Analysts and arms-control experts say it would be illegal for a country that bought the missile systems - the age, type, and designations of the weapons strongly indicate that they were sold to Saudi Arabia, according to three analysts who examined the videos - to transfer them to a third party without modifying the "end user" paperwork that's used to track international arms sales.

It remains uncertain if wider introduction of TOWs will reverse what have been successes by government forces, whose troops have scored major gains in recent months.