Published: Jun 14, 2013 9:05 AM EDT

BEIRUT (AP) - The Syrian government on Friday dismissed U.S. charges that it used chemical weapons as "full of lies," accusing President Barack Obama of resorting to fabrications to justify his decision to arm Syrian rebels. The commander of the main rebel umbrella group welcomed the U.S. move.
 
The U.S. decision to begin arming the rebels, though details have not been completed, marks a deepening of U.S. involvement in Syria's two-year civil war. It comes as President Bashar Assad's forces have been scoring victories, driving rebels out of a key town near the Lebanese border and launching offensives in the center and north, targeting Aleppo, the nation's largest city.
 
U.S. officials said the administration could provide the rebel fighters with a range of weapons, including small arms, ammunition, assault rifles and a variety of anti-tank weaponry such as shoulder-fired rocket-propelled grenades and other missiles. However, no final decisions have been made on the type of weaponry or when it would reach the rebels, according to the officials, who insisted on anonymity in order to discuss internal administration discussions with reporters.
 
In addition to the increased military aid, the U.S. also announced Thursday it had conclusive evidence that Assad's regime has used chemical weapons, including the nerve agent sarin, on a small scale against opposition forces. The White House said multiple chemical attacks last year killed up to 150 people.
 
Obama has said the use of chemical weapons cross a "red line" triggering greater U.S involvement in the crisis.
 
"The White House has issued a statement full of lies about the use of chemical weapons in Syria based on fabricated information," a statement issued Friday by the Syrian Foreign Ministry said.  "The United States is using cheap tactics to justify President Barack Obama's decision to arm the Syrian opposition," it said.
 
The commander of the main Western-backed rebel group fighting in Syria said he hoped that U.S. weapons will be in the hands of rebels in the near future,  noting it would boost the spirits of the fighters on the ground.
 
"We hope to have the weapons and ammunition that we need in the near future," Gen. Salim Idris told Al-Arabiya TV.
 
"This will surely reflect positively on the rebels' morale, which is high despite attempts by the regime, Hezbollah and Iran to show that their morale after the fall of Qusair deteriorated," he said, referring to the town near the border with Lebanon.
 
Assad's forces, aided by fighters from Lebanon's militant group Hezbollah, captured Qusair on June 5, dealing a heavy blow to rebels who had been entrenched in the strategic town for over a year.
 
Since then, the regime has shifted its attention to recapture other areas in the central Homs province and Aleppo to the north.
 
The regime's advances have added urgency to U.S. discussions on whether to provide the rebels with weapons.
 
The decision came a day after the United Nations said nearly 93,000 people have been confirmed dead in Syria's civil war, but the actual number is believed to be much higher.
 
Russia, a staunch ally of Assad, on Friday disputed the U.S. charge that Syria used chemical weapons against the rebels.
 
President Vladimir Putin's foreign affairs adviser, Yuri Ushakov, told reporters that the information provided by U.S. officials to Russia "didn't look convincing."
 
Alexey Pushkov, chairman of Russia's parliamentary foreign affairs committee, wrote on his Twitter account Friday that "the data on Assad's use of chemical weapons were faked in the same place as the lie about (Saddam) Hussein's weapons of mass destruction," referring to the deposed Iraqi dictator.
 
"Obama is going down the route of G. Bush," he added, in reference to former U.S. President George W. Bush's assertion - never proven, but used to justify the invasion of Iraq - that Saddam Hussein possessed weapons of mass destruction.
 
Obama's deputy national security adviser, Ben Rhodes, said Obama was planning to step up military assistance to Syrian rebels.
 
Ushakov warned that providing such assistance could derail efforts to convene a Syria peace conference. The main opposition coalition has already said it would not attend, all but scuttling the initiative.