ANTAKYA, Turkey (Reuters) - Rebel fighter Mustafa and his trio of burly men look out of place at a trendy Turkish cafe near the Syrian border, dressed in tattered jeans and silently puffing on cigarettes as they scoop into tall ice-cream sundaes.
Their battleground is across the frontier in Syria, where they are fighting to topple President Bashar al-Assad. But like many rebels in northern Syria, they are so desperate for weapons and money, they are searching for new donors in Turkey.
"When it comes to getting weapons, every group knows they are on their own," says the 25-year-old with a patchy beard. "It's a fight for resources."
Nominally Mustafa's rebels fight for the Free Syrian Army (FSA), but the FSA, lacking international recognition or direct state funding, is a often just a convenient label for a host of local armed groups competing fiercely for scarce financing.
So fiercely, they sometimes turn their guns on each other.
"Everyone needs weapons. There is tension. There is anger and yes, sometimes there is fighting if rebels in one town seem to have an unfair share of weapons," said Mustafa, who comes from Syria's northwestern province of Idlib, which borders Turkey and has been a hotbed of resistance to Assad.
Such mistrust is compounded by the competing agendas of outside parties who are further fragmenting the rebel movement.
Finding a donor usually means using personal connections, rebels say. They get relatives or expatriate friends to put them in touch with businessmen or Syrian groups abroad.
But once fighters go to private donors for weapons, they have to negotiate, and the price may be ideological.
Many say Islamist groups, from hard-line Salafists to the exiled Muslim Brotherhood, bankroll many battalions that share their religious outlook. The Brotherhood has representatives in Antakya ready to meet interested rebels, fighters say.
Leftist politicians and other opponents of Islamists are trying to counter that influence by funding rival armed bands.
"These groups are all making their own militias, like they are some kind of warlords. This is dividing people," said one activist who asked not to be named. "They aren't thinking about military strategies, they are thinking about politics."
With the U.N. peace plan for Syria on the ropes, Saudi Arabia and Qatar, regional rivals of Assad's main ally Iran, are likely to increase calls for the insurgents to be armed.
Western powers wary of military entanglement in another Middle Eastern hotspot have so far said this would not be helpful, while proposing non-lethal aid to the opposition.
Even if that were to change, it is not clear how military supplies could be directed to competing insurgents hopelessly outgunned by Assad's artillery and tanks, many of whom don't even agree on a military strategy.
Several rebel groups have formally broken with the FSA to form outfits such as the Syrian Liberation Army, the Patriotic Army and The Alternative Movement, whose real identity and clout are hard to assess, because the government restricts media access to Syria.
The FSA has pledged to honor the shaky U.N.-backed truce that took effect on April 16 if the army reciprocates. But the Syrian Liberation Army says it will keep fighting.
"We don't accept the ceasefire. We have slowed down a bit, only because we don't have enough weapons," its spokesman, Haitham Qudeimati, told Reuters.
Fighters say private donors, possibly frontmen for Gulf states such as Saudi Arabia and Qatar, have funneled millions of dollars to favored rebel groups. Many suspect the Muslim Brotherhood and the Salafis are getting the lion's share.
A 60-year-old rebel commander called Abu Shaham, from the central city of Hama, accused the Brotherhood of hanging back from the battlefront to overpower other rebel groups later.
"The Brotherhood is pumping money into the rebel units yet their men don't fight as much as us. They are almost always the first to retreat. Why?" he asked.
"They are not thinking about this phase in the battle. They care about what comes next. They want to save themselves for the struggle after Assad falls, to come out the strongest."
Analyst Joseph Holliday, of the U.S.-based Institute for the Study of War, said if foreign powers do not engage with the rebels in an orderly way, their rivalries could create chaos.
"If we don't recognize the rebels, anyone can set up shop in Turkey and start funding opposing groups," said Joseph Holliday, of the U.S-based Institute for the Study of War. "We don't know who is arming who ... I'm afraid by the time the West decides to do something it may be too late."
Some rebels worry Islamist radicals could stoke tensions between majority Sunni Muslims, who have driven the revolt, and minority Alawites, Shi'ites and Christians, who are wary of it.
"There are a lot of jihadists who want to come from abroad, this is real," said one insurgent, who asked not to be named. "Then we will no longer be talking about Syria's fight for freedom, we'll be talking about a sectarian war."
KILLING THE "FLEAS"
Qudeimati says most rebels do not belong to any unified group because of a culture of distrust, fostered by years of fear under Syria's infamous secret police.
"The problem is the Assad regime had 40 years to create mistrust between Syrians," Qudeimati said. "The lack of unity has been part of the regime's strategy."
Some FSA rebels say they even keep a distance from the FSA's top officers, fearing they too are infiltrated.
Suspicion of "fleas" - slang for collaborators - has bred an environment where vigilante killing almost seems the norm.
"There are a lot of groups on the ground working alone and not all of them are good guys," said rebel commander Abu Shaham.
"Some are thieves or criminals taking advantage of the chaos. So we go after the fleas and chase them out or kill them. We don't have a problem shooting these people."
Last month, the commander of a rebel unit in Homs province, Amjad al-Hameed, who claimed to be funded by The Alternative Movement, criticized the leaders of several other groups.
"We have armed men among our civilians that are a burden to our revolution," he told a crowd in a March 17 YouTube video. "They are just thieves ... It is impermissible for anyone to rape women, otherwise we are no different from Bashar al-Assad."
The next day, unidentified gunmen shot him dead.
Hameed's battalion did not blame the government but other rebels, vowing to "punish them as they deserve."
Some rebels adopt the FSA label simply to improve their chances of getting funds.
"We felt forced into aligning with the Free Syrian Army because it is the most widely known. If it gets recognized, we'll get foreign aid," says the Idlib rebel Mahmoud.
At a refugee camp in Turkey, Mahmoud and his eager comrades sit next to a muscular Syrian exile who discreetly shows them his laptop and chats with them about military strategy.
He won't say who has sent him or what he wants in return. But he hints there could be weapons on offer, joking: "I've come to help buy the boys their fruits and vegetables."
(Editing by Alistair Lyon)