By Andrew Quinn
WASHINGTON (Reuters) - The United States expelled Syria's top diplomat in Washington on Tuesday following what it described as the "despicable" massacre of more than 100 civilians in a Syrian town.
State Department spokeswoman Victoria Nuland said Syrian Charge d'Affaires Zuheir Jabbour had been given 72 hours to leave the country, part of a wave of expulsions of Syrian diplomats from Western capitals.
While the moves were symbolically important and aimed at increasing Syrian President Bashar al-Assad's isolation, the Obama administration continued to resist any U.S. military intervention in Syria.
The killings in the village of Houla, some of which the U.N. peacekeeping chief on Tuesday said bore the hallmarks of pro-Assad militias, have increased pressure on Western government to halt more than a year of bloodshed in Syria.
On the diplomatic front, Australia, Canada, France, Germany, Italy, Spain and the United Kingdom took similar steps against Syrian diplomats in those countries in a coordinated move.
"We took this action in response to the massacre in the village of Houla - (the) absolutely indefensible, vile, despicable - massacre against innocent children, women, shot at point-blank range by regime thugs, the Shabiha," Nuland told reporters, referring to pro-government militia.
In a separate statement, Nuland described Friday's attack on the town of Houla as a "vicious assault involving tanks and artillery - weapons that only the regime possesses."
"There are also reports that many families were summarily executed in their homes by regime forces," Nuland said.
"We hold the Syrian government responsible for this slaughter of innocent lives," Nuland said, calling the Houla attack "the most unambiguous indictment to date" of Damascus' refusal to implement U.N. resolutions calling for a peaceful resolution to the conflict.
Syrian officials have denied any army role in the massacre, one of the worst single incidents in the conflict.
The White House on Tuesday said again that it did not believe the time was right for military intervention in Syria, and rejected calls by Republican presidential candidate Mitt Romney for more direct steps to end Assad's rule.
"We do not believe that militarization, further militarization of the situation in Syria at this point is the right course of action. We believe that it would lead to greater chaos, greater carnage," White House spokesman Jay Carney said.
"POLICY OF PARALYSIS"
While the U.S. electorate is primarily focused on the economy, Romney, President Barack Obama's expected rival in the November U.S. presidential election, has sought to use the unresolved Syrian crisis to paint Obama as weak on foreign policy.
Romney issued a statement Tuesday criticizing what he said was the administration's "policy of paralysis" on Syria.
"We should increase pressure on Russia to cease selling arms to the Syrian government and to end its obstruction at the United Nations. And we should work with partners to arm the opposition so they can defend themselves," he said.
An Obama campaign official has called such criticism from the former Massachusetts governor "a cheap shot at the president's foreign policy without offering any realistic solutions of his own."
Syria's longtime ambassador to Washington, Imad Moustapha, was recalled late last year and a formal replacement has not been named, leaving Jabbour as Damascus' top representative in the United States.
The joint action against Syrian diplomats marked a potentially new phase in the struggling international effort to halt the repression of a 14-month uprising against Assad and force him to relinquish power.
Nuland said the United States had chosen not to expel the lower-level officials at the Syrian Embassy in Washington, describing them as "mid- and low-level functionaries."
The United States in February closed its embassy in Damascus, withdrawing Ambassador Robert Ford and all U.S. diplomatic personnel due to the worsening security situation in the country.
The step stopped short of severing diplomatic relations, however, and Ford and his team continue to work on Syria from Washington, seeking to maintain contact both with government officials and opposition activists.
Washington has already imposed tough sanctions on Damascus, but has been struggling to craft a more muscular international response to the crisis amid opposition from Russia and China, both permanent members of the U.N. Security Council.
(Additional reporting by Jeff Mason; Editing by Warren Strobel and Bill Trott)