U.S. Senator Robert Menendez, the chairman of the influential Foreign Relations Committee, introduced a bill on Monday that would provide weapons to some vetted groups of Syrian rebels.
Menendez, a Democrat, was one of a few senators pushing the White House to provide for lethal aid to some of the rebels fighting the government of Syrian President Bashar al-Assad even before reports that chemical weapons had been used on a small scale in the conflict.
It is not clear if the bill will become law. It would have to get through the committee and be approved by both the Senate and House of Representatives, and signed by President Barack Obama.
Menendez said reports that sarin gas was used in Syria increased the urgency for Washington to act.
"The Assad regime has crossed a red line that forces us to consider all options," Menendez said in a statement. "The greatest humanitarian crisis in the world is unfolding in and around Syria, and the U.S. must play a role in tipping the scales toward opposition groups and working to build a free Syria."
U.S. opponents of arming the Syrian rebels warn that weapons could find their way into the hands of anti-American extremists among the insurgents, such as the Nusra Front.
The bill, to be taken up in committee next week, excludes sales to the rebels of shoulder launched surface-to-air missiles known as MANPADS. After the Soviet Union invaded Afghanistan in 1979, the CIA, with Saudi backing, provided sophisticated shoulder-fired Stinger missiles to Islamic militants seeking to oust Soviet troops.
The missiles played a significant role in the Soviets' ultimate defeat in Afghanistan. But they also became a major headache for U.S. and other Western counterterrorism agencies when anti-Soviet militants morphed into anti-Western militant factions including al Qaeda.
Obama has said the United States will look at every option on how to deal with the civil war in Syria, which has killed more than 70,000 people and created more than 1.2 million refugees.
Among other things, Menendez's legislation would create a $250 million transition fund to help the civilian opposition in providing services and impose sanctions on arms and oil sales to Assad's government.
He said weapons would be sent to rebel groups that had gone through a vetting process and met standards on human rights, terrorism and non proliferation.
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