* More than 66,000 Syrian refugees now in Turkey
* Former Syrian PM in Qatar to discuss anti-Assad struggle
* Ahmadinejad says no room for Israel in new Middle East
By Tom Perry
BEIRUT, Aug 17 (Reuters) - Refugees are fleeing Syria in ever greater numbers, U.N. agencies said on Friday, as the conflict between President Bashar al-Assad's forces and rebels intensifies.
Former Syrian Prime Minister Riyad Hijab, who defected this month, has arrived in Qatar to discuss how to unify opposition efforts to hasten Assad's downfall, his spokesman said.
Hijab, a Sunni Muslim, is the most senior serving civilian official to desert Assad, whose ruling system is dominated by members of his Alawite sect, an offshoot of Shi'ite Islam.
Shi'ite Iran, Assad's closest ally, has cast the revolt in Syria as a plot by the United States and its regional allies to destroy an anti-Israel "axis of resistance" linking Tehran, Damascus and Lebanon's Shi'ite Hezbollah movement.
"You want a new Middle East? We do too, but in the new Middle East ... there will be no trace of the American presence and the Zionists," Iranian President Mahmoud Ahmadinejad said in a speech to mark annual state-organised rallies against Israel.
Saudi Arabia, Qatar and Turkey, which like Syria have mainly Sunni populations, are the principal regional supporters of the rebels fighting Assad in an increasingly bloody conflict.
More than 250 people, including 123 civilians, were killed in Syria on Thursday alone, according to the Syrian Observatory for Human Rights, a British-based opposition watchdog.
Turkey is taking the brunt of a swelling exodus of refugees, with 66,000 Syrians now sheltering there, the Turkish state disaster and emergency authority said.
Some 1,500 arrived from the rebel-held border town of Azaz after Assad's air force bombed it on Wednesday, killing at least 35 people, Turkey's Dogan news agency reported. It said another 1,500 from the devastated town were thought to be on their way.
Fighting has been raging in the northern city of Aleppo as rebels battle for control of Syria's biggest city. Assad's forces have turned increasingly to air power to hold back lightly-armed insurgents trying to seize territory elsewhere.
Turkey's state-run Anatolian news agency said 13 of 86 casualties brought from Aleppo and Azaz to a state hospital in the Turkish border province of Kilis had died from their wounds.
More than 170,000 Syrian refugees have been registered in Turkey, Jordan, Lebanon and Iraq, the U.N. refugee agency said.
"There has been a further sharp rise in the number of Syrians fleeing to Turkey," spokesman Adrian Edwards of the U.N. High Commissioner for Refugees (UNHCR) said in Geneva. Forty percent of those in Turkey had arrived this month, he added.
Humanitarian conditions in Syria have deteriorated as fighting worsens, cutting off civilians from food supplies, health care and other assistance, U.N. agencies say. Sewage-contaminated water has led to a diarrhoea outbreak in the countryside around Damascus, with 103 suspected cases.
Some 1.2 million people are uprooted within Syria, many staying in schools or other public buildings, U.N. officials say. U.N. humanitarian chief Valerie Amos, ending a visit to Syria, said on Thursday up to 2.5 million people needed aid in the country, scene of a 17-month-old revolt against Assad.
"PATH OF WAR"
Diplomats from the world's major powers, along with key Arab governments and Turkey, were due to meet at the United Nations in New York on Friday to discuss what to do after the failure of peace efforts led by U.N.-Arab League envoy Kofi Annan.
U.N. sources said veteran Algerian mediator Lakhdar Brahimi had agreed to take over from Annan, who resigned two weeks ago in frustration, but that he would pursue a new approach.
The last U.N. monitors are due to leave Damascus by Aug. 24, U.N. officials said, after a doomed mission to observe a ceasefire declared by Annan on April 12. It never took hold.
"It is clear that both sides have chosen the path of war, open conflict, and the space for political dialogue and cessation of hostilities and mediation is very, very reduced at this point," said deputy U.N. peacekeeping chief Edmond Mulet.
The U.N. Security Council remains deadlocked over Syria, with Russia and China resisting Western efforts to step up pressure on Assad to quit and unwilling to give even an amber light for military intervention - not that the United States and its allies have shown any appetite for overt action in Syria.
The war in Syria is fraught with danger for neighbouring countries such as Lebanon, where a local Shi'ite clan this week kidnapped more than 20 Syrians to try to secure the release of a kinsman seized by Syrian rebels near Damascus.
The gunmen said a Turkish hostage would be the first to die if their relative were killed.
Gulf Arab states have told their citizens to leave Lebanon after threats that more hostages would be seized.