US President Barack Obama, currently on a visit to Berlin, Wednesday refused to specify what military support America was providing rebels in Syria.
Obama, however, reiterated that the Syrian government forces had used chemical weapons in the civil war, Xinhua reported.
"I cannot and will not comment on specifics on our programmes related to the Syrian opposition," Obama said at a press conference with German Chancellor Angela Merkel.
He said Washington was confident that the Syrian government used chemical weapons and it was not possible for President Bashar al-Assad to regain legitimacy.
The US decided last week that Washington would ramp up its involvement in the Syrian conflict, following an American investigation that accused Syrian government forces of using chemical weapons.
In an interview to a German newspaper, Assad warned that Europe will "pay the price" if it was to send arms to rebel forces in his country.
Assad also denied claims that Syrian forces used chemical weapons in the conflict.
Around 93,000 people have been killed in the conflict that began in March 2011.
