By Michelle Nichols
NEW YORK (Reuters) - As Syria marks a decade of conflict the United Nations expressed "profound regret" on Monday that it has not yet been able to mediate an end to the civil war.
A crackdown on pro-democracy protesters by Syrian President Bashar al-Assad in 2011 led to civil war, with Russia backing Assad and the United States supporting the opposition. Millions of people have fled Syria and millions are internally displaced.
"I express the profound regret of the United Nations that we have yet not been able to mediate an end to this tragic conflict," U.N. Syria mediator Geir Pedersen told the U.N. Security Council on Monday.
Pedersen, who was appointed in late 2018, is the fourth person to lead U.N. efforts to end the Syrian war.
"The Syrian tragedy will go down as one of the darkest chapters in recent history – the Syrian people are among the greatest victims of this century," Pedersen said.
"They have been injured, maimed and killed in every way imaginable – their corpses even desecrated. ... They have endured the unspeakable horrors of chemical weapons," he told the 15-member body, which has been deadlocked over Syria with Syrian ally Russia and China pitted against Western members.
Russia has vetoed 16 Security Council resolutions on Syria over the past decade, backed by China for many of those votes.
"There's only one reason we have not been able to enact this solution and resolve this crisis: the Assad regime's refusal to engage in good faith," U.S. Ambassador to the United Nations Linda Thomas-Greenfield told the council. "So, we call on Russia to press the Assad regime to quit stalling."
Russia's U.N. Ambassador Vassily Nebenzia blamed "external forces" for tapping into the 2011 unrest in a bid to overthrow Assad's government and called for an end to unilateral sanctions on the country.
"We view a key precondition in the peace settlement to be the cessation of foreign occupation and military activities which have not been approved by the legitimate government of the country," Nebenzia said.
Islamic State also took advantage of the chaos to gain a foothold in Syria for some time. The United States and allies began military action against the group in 2014. Turkey still controls swaths of territory in Syria's northwest and the United States has a presence in the northeast.
U.N. Secretary-General Antonio Guterres said last week that Syria is a "living nightmare" where about half the children have never lived a day without war and 60 percent of Syrians are at risk of going hungry.
(Reporting by Michelle Nichols; editing by Jonathan Oatis)