Officials from the 27-nation European Union said they want the U.N. Human Rights Council to pass a resolution that is stronger than a draft tabled by Qatar, Turkey and the United States.
The 47-member rights council is holding an emergency meeting in Geneva on Friday to discuss the massacre in Houla, where the U.N. says at least 108 people - including 49 children under the age of ten - were killed last week.
"Mostly we are pressing for some stronger language on accountability," said Maria Ulff Moeller, a Danish diplomat whose country currently holds the rotating presidency of the European Union.
The current draft condemns the killings and states that "those responsible for serious violations of human rights must be held accountable," but doesn't suggest how. It also calls for an expert group to investigate the massacre, but that group has previously been blocked from entering Syria by President Bashar Assad's regime.
EU officials say they want the resolution to include a call for the U.N. Security Council in New York to consider referring the massacre to the International Criminal Court. This is something the rights council cannot do on its own. And since Syria isn't a member of the ICC, under international law only the Security Council can refer it to the Hague-based tribunal.
"We can encourage the Security Council to refer the situation to the ICC, and it's something we are pushing for," said Moeller.
Human rights groups backed the EU position. "At this stage what we need is a strong resolution requesting ICC referral," said Juliette de Rivero, a spokeswoman for the group Human Rights Watch.
Syria puts blame on oppositon
But Syria said its preliminary investigation had shown that anti-government armed groups carried out the massacre with the aim of encouraging foreign military intervention against the government.
Facing international outrage over the killings, Damascus launched its own investigation into the deaths and announced that special prayers for the victims would be held at mosques across the country on Friday.
At a news conference Thursday, Qassem Jamal Suleiman, who headed the government's investigation into the massacre, categorically denied any regime role. He said hundreds of rebel gunmen carried out the slaughter after launching a coordinated attack on five security checkpoints.
The aim, he said, was to frame the government and to ignite sectarian strife in Syria.
"Government forces did not enter the area where the massacre occurred, not before the massacre and not after it," he said, adding that the victims were families who refused to oppose the government or carry arms.
A Houla-based opposition activist said it was clear that there had been no government investigation.
"The regime is looking for ways to justify the massacre to the world," said Saria al-Houlany. "It's clear that there wasn't any professional probe. ... If we had 800 fighters in Houla, this massacre would not have happened," he said.
Foreign Ministry spokesman Jihad Makdissi said the aim was to create sedition in Syria.
"There are people in dark rooms working night and day to target Syria ... and the way to do it is to ignite civil strife," he told reporters at the same news conference. "They will not succeed."
Western nations said on Thursday that Syria was on the brink of full-blown sectarian civil war, and urged Russia to end its support for Assad and put pressure on him to stop the bloodshed.
The draft text condemns the killings as violating Security Council resolutions and accuses Syrian forces of "repeated and systematic violations of human rights".
It calls for an existing team of UN rights investigators to "conduct a comprehensive, independent and unfettered special inquiry consistent with international standards into the events in El-Houleh (Houla), to publicly identify those responsible for these atrocities and hold them to account".
But the EU is seeking stronger language on accountability - including a possible call for action by the UN Security Council - and has proposed amendments, according to diplomats.
"The bottom line is there is still debate over trying to get consensus or a stronger resolution," a Western diplomat said.
"The question is whether to try to keep the Russians on board or sacrifice some of the stronger language. Some would like to create a more pragmatic approach with an eye to New York ultimately," he said, referring to Russia's veto in the UN Security Council.
Russia is a staunch ally of the Assad government and one of its main weapons suppliers. A Russian cargo ship that Western officials say was heavily laden with weapons for the government of Syria docked at the Syrian port of Tartus last weekend, a rights group said on Thursday.
The United States and EU have suggested the Security Council should impose an arms embargo and other sanctions on Syria for its 14-month crackdown on anti-government protest in which more than 10,000 people have died.