-- Secretary of State Hillary Clinton bluntly warned Russia on Thursday that its support for Syria's Bashar al-Assad could help trigger a "catastrophic" civil war in Syria that risks spilling across the Middle East with devastating consequences.
"My argument to the Russians is — they keep telling me they don't want to see a civil war, and I have been telling them their policy is going to help contribute to a civil war," Clinton said in an interview with Denmark's TV2 during a visit to Copenhagen.
Russia — along with China — has blocked U.N. Security Council support for an Arab League plan to end Assad's bloody 15-month crackdown on opposition to his regime. The United Nations estimates that some 13,000 have died in the violence.
"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," Clinton said at a press conference with Danish Foreign Minister Villy Sovndal.
"They are just vociferous in their claim that they are providing a stabilizing influence. I reject that. I think they are, in effect, propping up the regime at a time when we should be working on a political transition," the top American diplomat charged.
Clinton's remarks could foreshadow a combative tone for President Barack Obama's planned meeting with Russian President Vladimir Putin on the sidelines of a G20 summit in Mexico June 18-19.
In Washington, U.S. officials pressed Moscow to halt any military shipments to Assad's government. "We believe that all countries should cease any and all military assistance with Assad's regime and we've repeatedly expressed those concerns with Russian officials both publicly, as I'm doing now, and privately," State Department spokesman Mark Toner told reporters Thursday.
The sharp escalation in Washington's pressure on Moscow to help end the bloodbath in Syria came as the White House accused Iran of "malignant behavior" by supporting the government in Damascus.
Obama's press secretary, Jay Carney, warned that time was running short for a peaceful, negotiated transition that eases Assad from power.
"The longer this goes on, the longer that Assad and his thugs are allowed to brutally murder the Syrian people, the more likely it becomes a sectarian civil war; the more likely that it spills over Syrian borders; the more likely that it transforms into a proxy war with different players, including, of course, Iran, which is already engaging in malignant behavior with regards to the Syrian situation, stepping up that kind of activity," he told reporters.
News of fresh atrocities like the reported massacre of civilians in Houla "horrifies" Obama but also "bolsters his resolve" to find a way to end the violence in Syria, Carney said.
"The brutality exhibited by Assad will surely doom him in history as a tyrant and a human rights violator and the worst kind of leader imaginable for any people," the spokesman said.
At the same time, "there is no question that as mighty as the United States is, that we cannot end all atrocities around the globe," Carney said.
Washington has said it will not provide arms to Syria's rebels but has effectively given the green light for other countries — notably Gulf nations — to do so.
At the same time, America and its allies have sought to sift through the Syrian opposition to determine who its key leaders are and where their allegiances lie. On Thursday, Carney seemed to vouch for the majority of the rebels, saying only "fringe" elements were aligned with Islamist extremists.
"We recognize and have said that there are elements to the Syrian opposition that do not share the democratic ideals of the broad Syrian people, who are not necessarily friends of the United States," he said.
"Those elements appear to us to be fringe elements. They do not represent the opposition as a whole. But we need to be mindful of that," Carney said.
"We believe that those who support al Qaeda or al Qaeda in Iraq and other elements are fringe elements of the opposition; that the broad opposition aspires to meet the democratic desires of the Syrian people," he said.
Toner emphasized the communication the U.S. has engaged in with Assad's opponents in Syria. "We've been working all along with the Syrian opposition, trying to improve their cohesiveness, trying to help them come together more as a cohesive body," Toner said. "We have seen progress."
"There's still a ways to go here, but we need to foster the Syrian opposition so that when this transition does come there is an adequate, functioning opposition to help shepherd this change," he said.
Clinton, in Copenhagen, played down the prospects of an imminent breakthrough deal among Washington and other world powers.
"We're nowhere near putting together any kind of coalition other than to alleviate the suffering," she said.
"We have to peel away the regime's continued support within Syria while bolstering our assistance to the opposition and by isolating the regime diplomatically and economically," she said.
More popular Yahoo! News stories:
Want more of our best political stories? Visit The Ticket or connect with us on Facebook, follow us on Twitter, or add us on Tumblr. Handy with a camera? Join our Election 2012 Flickr group to submit your photos of the campaign in action.