Syrians in the military and business who still support President Bashar Assad should turn against him, U.S. Secretary of State Hillary Rodham Clinton said Sunday.

"The longer you support the regime's campaign of violence against your brothers and sisters, the more it will stain your honor. If you refuse, however, to prop up the regime or take part in attacks on your fellow citizens, your countrymen and women will hail you as heroes," Clinton said at a news conference in Morocco as she conveyed a message to those holdouts backers of the embattled leader.

Syria's authoritarian government held a referendum on a new constitution Sunday, but the opposition deemed it an empty gesture and the West dismissed the vote as a "sham."

Activists estimate close to 7,500 people have been killed in the 11 months since Assad's crackdown on dissent began.

"Assad would have the Syrian people believe that it is only terrorists and extremists standing against the regime. But that is wrong," Clinton said. "So many Syrians are suffering under this relentless shelling. All Syrians should be working together to seek a better future."

Clinton was among the international officials who discussed the crisis during a conference Friday in Tunisia. They are trying to develop a united strategy to push Assad from power and they began planning a civilian peacekeeping mission to deploy if his government falls.

She said in the Moroccan capital that "we're appealing to members of the Syrian army to put the people of their country first before a family or a political party. And we are pushing hard for a plan that would lead to a political transition."