(CBS/AP) COPENHAGEN, Denmark - Secretary of State Hillary Rodham Clinton on Thursday said Russia's continued support for Assad "is going to help contribute to a civil war."
In pointed remarks in Denmark on the first stop of a European tour, she recounted her discussions with Russian officials and criticized Moscow's rationale for opposing sanctions and other forms of pressure against the Assad government.
"The Russians keep telling us they want to do everything they can to avoid a civil war, because they believe that the violence would be catastrophic," she said, noting that they are "vociferous in their claim that they are providing a stabilizing influence.
"I reject that," she said, complaining that in fact, Russia was propping up Assad's regime. Some 13,000 people have died in 15 months of uprisings.
The calculus doesn't appear to be changing. Despite joining Western powers earlier this week in condemning the Houla killings, Russia has stood by its opposition to any outside military intervention. Instead, Moscow is urging all sides to focus on U.N. mediator Kofi Annan's peace plan, which by all accounts has failed to stem the violence.
Clinton also laid out the clearest case yet for why the Obama administration is reluctant to intervene militarily in Syria especially given Russia's stance even as it expresses revulsion over last week's massacre of more than 100 people in the town of Houla.
Clinton said Russia and China would have to agree before the U.S. and other nations engage in what could become a protracted conflict in support of a disorganized rebel force. And she cited a host of other hurdles to successful military action.
"We're nowhere near putting together any type of coalition other than to alleviate the suffering," Clinton told reporters after meeting with top officials in Denmark, a key contributor to last year's NATO-led mission against Muammar Qaddafi in Libya. "We are working very hard to focus the efforts of those, like Denmark and the United States, who are appalled by what is going on, to win over those who still support the regime, both inside and outside of Syria."
In remarks to Danish students, Clinton said every day of slaughter in Syria was strengthening the case for tougher international action. But she stressed that such action, including military action, would require support from Syria's ally, Russia, and the rest of the world community. Russia and China have twice vetoed U.N. Security Council sanctions against President Bashar Assad's regime.
Dennis Ross, a former American diplomat and top adviser to President Obama's administration on the Middle East, said the broader Arab world should exert pressure on Russia to change its stance against forced regime change.
In the meantime, the long-time diplomat says the U.S. must start to consider and plan for a means by which ainside northern Syria.
"We need to start planning for it," said Ross, adding that such a bold move - which would likely entail some foreign troop presence on Syrian soil - may be necessary to convince Assad his days in power are coming to an end. In Ross' own words, it would change the "psychological balance of power."
Clinton threw her support once again behind the U.N. mediation efforts Thursday, despite acknowledging that "thus far Assad has not implemented any of the six points that are part of Kofi Annan's plan."
She stressed that U.N. observers have nonetheless performed two important functions.
"In many of the areas where they are present, violence has gone down," Clinton said. "And they serve as independent observers, the eyes of the world if you will, in reporting back when terrible events like the recent massacre occur. They've tried to cut through the clutter and disinformation coming from the Syrian government."
She spoke as activists reported more shelling in the central Houla area, where 108 people, most of them women and children, were massacred last week.
The Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees activist groups said Thursday's shelling of Houla was mostly by heavy machine guns. Survivors of last week's Houla massacre blamed pro-regime gunmen for the close-range shooting of civilians in their homes, though the government has denied the involvement of its troops.
Damascus claimed Thursday it had investigated the massacre, and accused armed groups -- paid by regional and Arab states -- of carrying out the killings to incite a civil war in the country, reports CBS News' George Baghdadi.
"We absolutely deny any involvement and we confirm that the Syrian government cannot commit such an ugly crime," Syria's Foreign Ministry spokesman Jihad Maqdisi said at a televised press conference, promising to bring the assailants into trail who were aiming at "inciting a sectarian strife."
The Obama administration has called on Assad to step down and clear the way for a political transition. But mindful of a war-weary American public, it has stopped short of advocating direct U.S. military engagement in the country and stressed the need for diplomacy, particularly with Moscow, which continues to sell weapons and provide political support to the Assad regime.
On the first leg of a weeklong trip to Europe, Clinton recited a list of hurdles to armed intervention besides Russian reticence.
She said Assad's opposition lacks the unity that the anti-Gadhafi camp eventually rallied in Libya. Syria's professional military and substantial air defenses also would make intervening far more difficult. And whereas in Libya the U.S. was able to count on the support of Gulf countries in monitoring a no-fly zone and carrying out some airstrikes, the Arab League is split on whether military options should be entertained in Syria.
Clinton also warned about the danger of Syria's unrest spiraling into a larger civil war, which could morph into a proxy war that draws in Iran and other regional powers. She cited Jordanian concerns about its territory, Turkish worries over Kurdish terrorists operating from inside Syria and neighboring Lebanon's long struggle to emerge from decades of sectarian civil war and political instability.
"We know it could actually get much worse than it is," Clinton said. "We are trying to prevent that."
But she said doing nothing wasn't an option, either.
Clinton said nations must work together to "peel away the regime's continued support within Syria, while bolstering our assistance to the opposition and isolating the regime diplomatically and economically."
"There is still a fear among many of the elements of the Syrian society and the Syrian government that, as bad as the Assad regime is, it could get worse," Clinton said.