U.S. President Barack Obama is gearing up to send lethal weapons to the Syrian opposition, according to senior administration officials speaking to The Washington Post on Wednesday.
The officials said Obama was also tightening ties with allies seeking the ouster of Syrian President Bashar al-Assad, and the U.S. would be taking a “more aggressive” leadership role among the allies.
Obama is likely to make a final decision on the supply of arms to the opposition “within weeks,” The Post reported, citing the unnamed officials.
On Monday, Obama spoke with Russian President Vladimir Putin, discussing chemical weapons use. 
The report on Wednesday stated the U.S. administration “has launched an effort to convince Putin that the probable use of chemical weapons by the Syrian government … should lead him to reconsider his support of Assad.”
In a conference on Tuesday, Obama warned against a rush to judgment on Syria’s use of chemical arms, but said proof of their use would trigger a “rethink” of his reluctance to use military force.
As critics complain that he let Syria cross a U.S. “red line,” Obama said Washington believed chemical weapons had been used in the country’s vicious civil war but did not know exactly who had fired them.
“I’ve got to make sure I’ve got the facts. That’s what the American people would expect.”
“If I can establish in a way that not only the United States but also the international community feel confident in the use of chemical weapons by the Assad regime, then that is a game changer,” he warned.
“By game changer, I mean we would have to rethink the range of options that are available to us.”
“There are options that are available to me that are on the shelf right now that we have not deployed, and that’s a spectrum of options,” Obama said, saying he had asked the Pentagon for plans, but did not divulge them.
“We’re clearly on an upward trajectory,” an unnamed U.S. senior official told the Washington Post. “We’ve moved over to assistance that has a direct military purpose.”
The officials did not specify what U.S. equipment is under consideration, although the opposition fighters have specifically requested ¬antitank weapons and surface-to-air missiles, the Post reported.