Syria's main opposition group on Sunday welcomed a decision by Arab and Western governments to boost their assistance to rebel fighters but said more such moves were needed to end the 27-month conflict.

"The Syrian National Coalition thanks the (Friends of Syria) countries for their decisions, and welcomes the assistance that they pledged," the group said.

"More steps of this decisive nature remain necessary, in order to end the conflict quickly, to stop Syrians' blood from being spilt, and to make sure their aspirations are fulfilled."

The National Coalition said that it regretted that the decision to boost assistance to the rebels had not come sooner.

It said "thousands of... lives could have been saved," had the decision been taken earlier.

The opposition's statement came a day after Qatar said the Friends of Syria had agreed on a "secret" plan to ramp up assistance to the rebels.

At the meeting in Doha, US Secretary of State John Kerry pledged new support for the rebels to end an "imbalance" in President Bashar al-Assad's favour.

The National Coalition did not have an official delegation at the meeting.