ISTANBUL (Reuters) - The Secretary of State Hillary Clinton urged Syrian President Bashar al-Assad on Thursday to hand over power and leave his country, condemning a massacre near the town of Hama that opponents have blamed on his supporters as "unconscionable".
Clinton said the United States was willing to work with all members of the U.N. Security Council, which includes Russia, on a conference on Syria's political future as long as it started with the premise that Assad gave way to a democratic government.
"Assad must transfer power and depart Syria," Clinton told a news conference in Istanbul after meeting foreign ministers from Arab and Western nations to discuss counterterrorism.
"The regime-sponsored violence that we witnessed again in Hama yesterday is simply unconscionable. Assad has doubled down on his brutality and his duplicity and Syria will not, cannot be peaceful, stable or certainly democratic until Assad goes."
United Nations observers have been prevented from reaching the village of Mazraat al-Qubeir, near Hama where anti-Assad activists say Syrian troops and militiamen loyal to the president massacred at least 78 villagers, the head of the monitoring mission said on Thursday.
The reported carnage came hours before a divided U.N. Security Council discusses Syria.
The latest killings will heap pressure on world powers to act, but they have been stymied by divisions pitting Western and most Arab states against Assad's defenders in Russia, China and Iran.
Clinton urged the international community to unite behind an "achievable" plan and said Washington was willing to cooperate with any state as long as they agreed that Assad had to cede power.
"We are prepared to work with any country, including all members of the U.N. Security Council and we will do so, so long as any such gathering starts from the basic premise that Assad and his regime must give way to a new, democratic Syria."
Clinton said she would send her special adviser on Syria to Moscow on Friday to discuss with the Russian government the need for political transition in Syria.
She suggested that peace envoy Kofi Annan's plan, whose central plank was a ceasefire that never took hold, needed to be given a last chance, saying other nations - presumably Russia and China - would not support stronger action unless its failure was incontestable.
"We think it is important for us to give Kofi Annan and his plan the last amount of support that we can muster because, in order to bring others into a frame of mind to take action in the Security Council, there has to be a final recognition that it's not working," Clinton said.
Asked about upcoming nuclear talks between Iran and Britain, France, Russia, China, the United States and Germany - otherwise known as the P5+1, in Moscow on June 18, Clinton said Tehran needed to be prepared to take "concrete steps".
"We want them to come prepared to take concrete steps, particularly in the area of 20 enrichment," Clinton said.
Iran is refining uranium to 20 percent of fissile purity - well above the level required to run nuclear power plants - for what it says will be fuel for a medical research reactor.
But Western officials are worried because the 20 percent level hurdles major technical barriers to reaching the 90 percent - or bomb-grade - threshold and they believe Iran is stockpiling more material than it needs for nuclear medicine.
Additional reporting and writing by Jonathon Burch; Editing by Mark Heinrich