* Assad risks plunging Syria into civil strife - U.S. ambassador
* Police killed by armed terrorist groups - state news agency (Adds residents saying army defections and fighting in south)
By Khaled Yacoub Oweis
AMMAN, Sept 22 (Reuters) - Snipers killed two people in the Syrian city of Homs on Thursday, where tensions have emerged between its mostly Sunni inhabitants and the Alawite minority since troops stepped up raids to crush pro-democracy protests, residents said.
Directly addressing the sectarian issue for the first time, the United States said President Bashar al-Assad risked plunging Syria into civil strife by intensifying a crackdown on the uprising which began six months ago.
"The government violence is actually creating retaliation and creating even more violence in our analysis, and it is also increasing the risk of sectarian conflict," the U.S ambassador to Syria, Robert Ford, told Reuters by telephone from Damascus.
Assad is a member of Syria's minority Alawite sect who has ruled the mainly Sunni Muslim country since succeeding his late father Hafez al-Assad 11 years ago.
The official state news agency said five members of the security police were killed when their bus was ambushed by "armed terrorist groups" in the southern province of Deraa.
A local activist said a state hospital in Deraa morgue received several bodies of dead security personnel who were killed in fighting that broke out among an army unit positioned at a roadblock between towns of Museifera and Jeza after 25 conscripts among them defected.
"The fate of the 25 is unknown. We heard that more bodies had arrived to other hospitals," he said.
Security police, from Military Intelligence of Air Force Intelligence, are drawn mostly from Assad's Alawite sect. They usually accompany Sunni conscripts who man roadblocks erected by the military to restrict movement among towns and villages whose residents have taken part in the uprising, residents said.
Deraa, on the border with Jordan, was the first region where Assad sent troops and tanks in April, storming the provincial capital, to contain street protests. Military assaults have expanded since then to the coast and into the interior, including Homs, Syria's third largest city.
The two people killed in Homs on Thursday were middle-aged men, local activists said, adding that they were shot as they left mosques in the Sunni Khaldiya and Bayada quarters.
"Assad's response to the protests turned markedly bloodier this month," said one of the activists, who gave his name as Abu Yazan. "I think there is a realisation in Homs that no one will win if the regime manages to ignite sectarian strife."
Prominent figures from Alawite and Sunni areas of Homs and the surrounding countryside have been meeting to prevent a deterioration in relations, he said.
He cited a recent statement by three leading members of the Alawite community that said the minority's future was not tied to the Assads remaining in power.
Assad has promised reform and has changed some laws, but the opposition said they made no difference, with killings, torture, mass arrests and raids intensifying in recent weeks.
The 46-year-old president has repeatedly said that outside powers were trying to divide Syria under the guise of wanting democracy due to Damascus's backing for Arab resistance groups.
Assad has also said that the use of force to control the unrest is legitimate. Authorities say 700 police and army have been killed by terrorists and mutineers.
Lured by jobs in the state and security apparatus, Alawites have moved into Homs since Assad's father took power in a 1970 coup. The population of Homs and surrounding areas is now nearly one million.
The Syrian Observatory for Human rights said that Mohammad Saleh, a 54-year-old political prisoner who had been helping to calm tensions in Homs, was arrested on Thursday.
Saleh, who has already spent 12 years in prison, met a Russian parliamentary delegation which went to Homs on a tour organised by the authorities this month and "explained the suffering of the city", the British-based Observatory said in a statement.
Activists also reported the arrest of at least 80 villagers in the rural region of Houla north of Homs and in the province of Idlib on the border with Turkey in the northwest.
Troops have been raiding villages in the two regions in pursuit of defectors from the mostly Sunni army, which is commanded by officers largely drawn from the Alawite sect.
Ford said there had been more defections from the army since mid-September, but the military was "still very powerful and very cohesive". He said there were signs of dissent among the Alawites and the economy was in a sharp retreat.
"Most of the violence, according to our information, is coming from the government and its security forces. That can be either be shooting at peaceful protests or funeral procession or when government forces go into homes. We have had recently a number of deaths in custody, or extra-judicial killings," the ambassador said.
After a series of piecemeal measures, European governments have acted vigorously in recent weeks to tighten the screws on Assad in the hope of curbing his crackdown, which has killed about 2,700 people, including 100 children, the United Nations says.
Traders and analysts say Syrian oil exports have come to a halt due to sanctions and this may force a cut in production, weakening Assad's ability to generate cash but not threatening his grip on power yet.
Turkey said on Wednesday that it had suspended talks with Syria and may impose sanctions on Damascus, after failing to persuade Assad to stop the crackdown. (Additional reporting by Suleiman al-Khalidi, Dmitry Zhdannikov and Jessica Donati in London; Editing by David Stamp)
Our Standards: The Thomson Reuters Trust Principles.