Marrakech, Morocco — Western and Arab nations sympathetic to Syria's uprising against President Bashar al-Assad gave full political recognition on Wednesday to the opposition, reflecting a hardening consensus that the 20-month-old uprising might be nearing a tipping point.

Meeting in the Moroccan city of Marrakech as rebels battled Assad's troops on the outskirts of his Damascus power base, the "Friends of Syria" group called on Assad to step aside and warned him against using chemical weapons.

The meeting began less than a day after President Obama said the United States would join a handful of other Western and Arab countries in recognising the rebellious National Coalition of Syrian Revolutionary and Opposition Forces as the country's sole legitimate representative -- a diplomatic gambit that had been widely anticipated.

At the same meeting, the leader of Syria's opposition coalition called on the Alawite minority to launch a campaign of civil disobedience against Assad, an Alawite who faces a mainly Sunni Muslim uprising against his rule.