* Ambassador to Iraq defects, first envoy to jump ship
* Security Council divided over sanctions threat
* Russia's talks with Syrian opposition end in discord (Updates with quotes from Fares)
By Mariam Karouny
BEIRUT, July 11 (Reuters) - Syria's ambassador to Iraq defected on Wednesday in protest over President Bashar al-Assad's violent suppression of a 16-month uprising as the U.N. Security Council remained deadlocked over the next steps in the crisis.
"I declare that I have joined, from this moment, the ranks of the revolution of the Syrian people," Nawah al-Fares said in a video statement posted on Facebook. He did not elaborate or say from where he had posted the statement.
"I ask ... the members of the military to join the revolution and to defend the country and the citizens. Turn your guns toward the criminals from this regime," Fares said.
"Every Syrian man has to join the revolution to remove this nightmare and this gang which has reeked corruption across Syria and destroyed the state and society over the last 40 years, and to guarantee a bright future for the coming generations."
Fares, who has close ties to Syrian security, was the first senior diplomat to quit the embattled government.
He did not spell out his reasons for defecting, but repeatedly said government forces have been killing civilians.
There has been no comment from Damascus or Baghdad and the White House said it was unable to confirm the defection, hailed by Assad's opponents as a sign of crumbling support.
Assad's chief backer on the U.N. Security Council, Russia, remained firmly in the Syrian leader's camp. And the 15-member council made little headway after international mediator Kofi Annan asked it to agree on "clear consequences" if the government or opposition fail to comply with his faltering plan for a political solution to the crisis.
Fares, a Sunni Muslim and who had held senior positions under the late president Hafez al-Assad, is from Deir al-Zor, the eastern city on the road to Iraq which has been the scene of a ferocious military onslaught by Assad's forces.
"This is just the beginning of a series of defections on the diplomatic level. We are in touch with several ambassadors," said Mohamed Sermini, a member of the main opposition umbrella group, the Syrian National Council.
The defection of Fares could be a major blow to Assad, who wants to convince a sceptical world he is conducting a legitimate defence of his country against foreign-backed armed groups bent on toppling the government.
Fares' decision to jump ship follows the high-profile flight from Syria last week of Brigadier General Manaf Tlas, also a Sunni and once a close friend of Assad, whose minority Alawite sect has relied on Sunni allies to maintain control of Syria's majority Sunni population.
Tlas fled to Paris and has not spoken since of his intentions. Opposition sources said earlier that Fares was leaving Iraq but it was not clear where he would go.
"The apparent decision of yet another senior Syrian official to ditch Assad would be a chink in his armor," said one U.S. official, speaking on condition of anonymity.
"Although Ambassador Fares is not a member of Assad's inner circle, he's a respected Sunni figure and such a courageous act could help sway other Sunni elites to follow in his footsteps."
DIVIDED ON SANCTIONS
The apparent crack in Assad's diplomatic ranks came as international diplomacy inched along, plagued by divisions over what the next steps should be to address Syria's crisis.
Annan, appointed mediator by the United Nations and the Arab League, briefed the Security Council by video link from Geneva on the results of this week's diplomatic shuttle to Damascus, Tehran and Baghdad - three capitals forming a Shi'ite Muslim axis of power in the Middle East.
The deeply divided council must decide the future of a U.N. observer mission in Syria, known as UNSMIS, before July 20 when its 90-day mandate expires. It initially approved 300 unarmed military observers to monitor an April 12 ceasefire, which failed to take hold, as part of Annan's peace plan.
"He (Annan) called for the Security Council members to put aside their national interests and to put joint and sustained pressure on both parties with clear consequences for non-compliance," Britain's U.N. Ambassador Mark Lyall Grant said.
Russia and China, both veto-wielding permanent council members, have for months blocked moves by western and Arab countries aimed at increasing the pressure on Assad, leaving the council deadlocked.
Britain on Wednesday circulated a draft resolution to extend the monitors' mandate for 45 days and make compliance with Annan's transition plans for the country enforceable under Chapter 7 of the U.N. Charter, which allows the council to authorize actions ranging from diplomatic and economic sanctions to military intervention.
The draft resolution in particular threatens the Syrian government with sanctions if it does not stop using heavy weapons and withdraw its troops from towns and cities within 10 days of the adoption of the resolution.
The British text, drafted in consultation with the United States, France and Germany, counters a draft resolution circulated by Russia on Tuesday, which would extend UNSMIS for three months but makes no threat of sanctions.
Russia's Deputy U.N. Ambassador Alexander Pankin told reporters after Annan's briefing that Moscow believed sanctions were a "last resort".
IRAN, IRAQ SUPPORT
Annan said on Wednesday both Iran and Iraq supported a plan for a Syrian-led political transition in Damascus - buttressing his argument that Tehran should be involved in efforts to find a peaceful solution to the crisis despite the West's firm rejection of any Iranian role.
"Obviously, they will use their influence on the government and the parties in moving in that direction," he said.
But while Russia and China have also called for Iran to be included in the process, U.S. officials said there was still no sign that Tehran was ready to act constructively.
"Iran is definitely part of the problem in Syria. It is supporting, aiding and abetting the Assad regime materially and in many other ways and it has shown no readiness to contribute constructively," U.S. Ambassador to the United Nations Susan Rice told reporters.
Opposition leaders say there can be no peaceful transition unless Assad, who crushed popular protests from the moment they began, relinquishes power first. Assad, whose family has ruled Syria for 42 years, says he still has the backing of his people.
In Moscow, Syrian opposition talks with Russia ended in discord on Wednesday, and an opposition leader accused Moscow of pursuing policies that were helping to prolong the bloodshed in the country..
"The Syrian people don't understand Russia's position. How can Russia keep supplying arms? How can they keep vetoing resolutions? There needs to be an end to mass killings," said Burhan Ghalioun of the exiled Syrian National Council (SNC).
But one member of Syria's opposition said a broader shift may be starting in Moscow, which has stepped up its diplomacy in recent weeks amid hints it may be moderating its support for Assad as turmoil engulfs its long-time ally.
"We're trying to work out what exactly Russia is trying to do here. I think they're looking for a genuine solution," a member of the SNC delegation which held talks in Moscow said, asking not to be identified.
Assad's opponents say just under 13,000 armed and unarmed opponents of Assad, and around 4,300 members of security forces loyal to Damascus, have been killed since he launched a crackdown 16 months ago, using tanks and helicopter gunships to attack rebel strongholds inside Syria's biggest cities.
Activists on Wednesday reported a new bombardment of rebel areas of Homs, a hotbed of opposition to Assad, as well as fighting in many other parts of the country. State media reported on missile tests, part of war games that analysts say are a warning to Assad's foes.
Opposition figures have been calling for a no-fly zone and NATO strikes against Syrian forces, similar to those carried out in Libya last year which enabled rebel ground forces to end the rule of Muammar Gaddafi.
But while Assad has faced sanctions and international condemnation, major Western and Arab powers have shied away from the idea of direct military action.
(Additional reporting by Ben Blanchard in Beijing, Michelle Nichols at the United Nations, Mariam Karouny in Beirut, John Irish in Paris, Stephanie Nebehay and Tom Miles in Geneva and Tabassum Zakaria in Washington.; Writing by Douglas Hamilton, Andrew Quinn and Todd Eastham; Editing by Jackie Frank and Christopher Wilson)