WASHINGTON — The United States Wednesday dismissed Syria's call for a referendum on a new constitution, which critics see as a move designed to ease global outrage over the government's bloody crackdown.

"It's actually quite laughable -- it makes a mockery of the Syrian revolution," White House spokesman Jay Carney told reporters aboard Air Force One.

"Promises of reforms have usually been followed by an increase in brutality and have never been delivered upon by this regime since the beginning of peaceful demonstrations in Syria."

Syrian President Bashar al-Assad called the referendum a day after his country flatly rejected UN allegations of crimes against humanity.

The proposed charter drops Article 8 which declared the ruling Baath Party as the "leader of the state and society."

Under the newly drafted constitution, freedom is "a sacred right" and "the people will govern the people" in a multi-party democracy, state television said.

Assad, who in April scrapped emergency rule in force since 1963 when the Baathists took power, has made repeated promises of reforms that have failed to materialize since a popular uprising erupted on March 15 last year.

State Department spokeswoman Victoria Nuland also dismissed the referendum announcement.

"It looks like he's putting forward a piece of paper that he controls to a vote that he controls in an effort to try to maintain control," Nuland said.

"And it's frankly not working in any other capacity, so we don't think this is going to work either. He knows what he needs to do if he really cares about his people," Nuland said.

"The violence just needs to come to an end, and he needs to get out of the way so we can have a democratic transition."

Assad's decision came as activists said troops stormed the central city of Hama and stepped up assaults nationwide, despite mounting Arab and Western peace efforts.

Further to the south, an explosion struck an oil pipeline at daybreak in the flashpoint city of Homs, with activists saying government forces bombed it from the air and state media blaming "armed terrorist gangs."

Rights groups say more than 6,000 people have been killed since Assad's forces began cracking down on democracy protests launched 11 months ago.