By Andrew Quinn
WASHINGTON (Reuters) - Senators on Tuesday called on the Obama administration to impose tough new sanctions on Syria's energy sector as Washington sought to put muscle behind its demand that President Bashar al-Assad halt his lethal crackdown on unarmed protesters.
"The United States should impose crippling sanctions in response to the murder of civilians by troops under the orders of President Assad," Senator Mark Kirk, a Republican, said in introducing legislation to target firms that invest in Syria's energy sector, purchase its oil or sell gasoline.
Kirk was joined in sponsoring the bill by Democratic Senator Kirsten Gillibrand and independent Senator Joseph Lieberman, who said it was time to push for "a democratic transition that reflects the will of the Syrian people."
As the United States weighed its next steps to respond to Assad's escalating suppression of protests, Secretary of State Hillary Clinton met with representatives of Syria's fledgling opposition who said the battered pro-democracy movement badly needed stronger U.S. support.
"We really need to see President Obama addressing the courage of the Syrian people," said Mohammad Alabdalla, one of the U.S.-based activists who met Clinton.
"We want to hear it loudly and clearly that Assad has to step down."
Obama and Clinton have said Assad has lost legitimacy, but have stopped short of directly calling on him to leave office as they did Egypt's Hosni Mubarak and Libya's Muammar Gaddafi.
Political analysts said Clinton's meeting, coming amid gradually rising international pressure on Damascus, indicated Washington may move to a tougher stance on Assad.
Steven Heydemann, a Middle East expert at the U.S. Institute of Peace, said U.S. officials hoped to boost contact with the Syrian opposition without appearing to mastermind the demonstrations.
"There is a lot that the U.S. can do very quietly to facilitate coordination among segments of the opposition," Heydemann said. "But we can be most effective if we play these kinds of roles very quietly."
Rights groups have criticized Washington for failing to take strong steps on Syria, where activists say some 1,600 people have been killed as the government seeks to crush protests inspired by "Arab Spring" movements across the Middle East and North Africa.
Outrage has sharpened this week as Syria violently suppressed protests in the city of Hama, where tanks were sent to shell civilian neighborhoods and at least 122 people were killed since Sunday.
U.S. officials say they have limited leverage with Damascus after years of estrangement and need a stronger international consensus, particularly among Arab states, before discussing next steps. They also say Syrians themselves must decide what the future will look like.
"The democratic transition is under way. The Syrian opposition needs to identify how that transition should proceed. That should not be an American responsibility," U.S. Ambassador to Syria Robert Ford told a Senate hearing on Tuesday.
The U.N. Security Council negotiated for a second day on Tuesday over a Western-backed draft resolution condemning Syria, before adjourning until Wednesday.
Diplomats said significant differences remained over the text and it had not been decided whether the end result should be a resolution or a less weighty council statement.
Russia and some other countries are pushing for what they say is a more balanced text that would blame both Syrian authorities and the opposition for the violence, but Western nations say the two sides cannot be equated.
The United States has already imposed sanctions on Assad and members of his government, and says it is weighing new sanctions including possibly on its oil and gas industry.
The bipartisan group of senators said on Tuesday it was time to act against Syria's energy sector which, through oil revenues, provides about one-third of its export revenue.
"Until the Assad regime responds to the democratic urging of its people ... Syria will not have any access to the global economy and neither will any company doing business with Syria," Gillibrand said in a statement.
The Syrian activists who met Clinton on Tuesday said energy sanctions could interrupt funding for security forces and armed gangs controlled by Assad.
"The gas income is being used to fund some terrorist groups and to oppress the people of Syria. We want to stop that as soon as possible," opposition activist Marah Bukai said.
Ford, in his Senate testimony, said the United States was working with Canada and European countries -- whose companies are big players in Syria's energy sector -- to ensure that any new sanctions have the desired impact.
"I think the Syrian government's latest actions will help trigger action," he said.
(Additional reporting by Malathi Nayak; editing by Warren Strobel and Anthony Boadle)