* Separatists outnumbered and outgunned
* No public response to calls for weapons
* Ukrainian army advancing in the east
By Aleksandar Vasovic
DONETSK, Ukraine, July 30 (Reuters) - Western leaders may be Vladimir Putin's biggest critics over the conflict in east Ukraine but the Russian leader is also facing criticism from some of the rebels they accuse him of arming.
The European Union and the United States have imposed new sanctions on Russia because they say Putin has not done enough to persuade the pro-Russian separatists to stop fighting and is supplying them with weapons.
But there is also frustration with Putin among some of the fighters, even though a rebellion that began with assault rifles, hunting guns and old weapons now has multiple rocket launchers, self-propelled howitzers, armoured vehicles and tanks.
Squeezed by the Ukrainian army into their last two strongholds, the cities of Donetsk and Luhansk, the rebels complain they are outnumbered and outgunned.
"Oh, how we would like to see the Russian army here," said a fighter who gave his name only as Pavel, standing outside the rebel headquarters in Donetsk, an industrial city about 80 kilometres (50 miles) northeast of the nearest border crossing with Russia.
"If they were here, the Ukrainian border would be 300 km away to the west and south. But they're not coming."
Despite the denials of other rebels, he said the separatists were receiving military equipment, including multiple missile launchers, from Russia.
"But that's only a fraction of what we need. We need people, experienced people. But Putin is afraid of spending Russian funds and his oligarchs' funds," he said.
Another rebel fighter, who declined to give his name, also voiced frustration with Moscow.
"Russia must enter Novorossiya," he said, using the name - which means New Russia - that Putin himself has at times used for the regions in eastern Ukraine where the separatists have risen up against Kiev's rule.
"This is Russian soil, and every day they waste waiting (to send in arms and personnel) means more deaths," he said. "We feel somewhat as if we are Russia's cannon fodder."
It is not clear how widespread such disenchantment is among the rebels, and none of those who voiced criticism was prepared to give their full names for fear of retribution.
APPEAL FOR HELP
The leaders of the self-proclaimed Donetsk People's Republic, some of whom are Russian, dismiss talk of divisions in the ranks, including over Russia's role in the crisis.
But in May, Igor Girkin, a rebel commander who also goes by the name of Igor Strelkov, appealed for military assistance in comments that were widely viewed online.
There was no public response from Putin, and the rebel leadership has since said all the fighters' weapons come from military depots they seized in fighting.
The rebel leaders have sought to douse expectations that there will be any overt response.
"We are receiving constant political and humanitarian support from Russia ... Political support is the most important one," said Vladimir Antyufeyev, one of the top rebel officials.
"We would want to see that kind of (military) aid from Russia, but there will be none," he told a news conference.
Such comments have prompted grumbling by some of the rebels since a big push began by the Ukrainian army, forcing the separatists out of several towns including the city of Slaviansk, which had been one of their main strongholds.
Some of the Ukrainians who still hold prominent positions in the rebel ranks have also at times quietly criticised the Russians brought in to lead the rebellion.
"There are indications that some groups feel betrayed by Moscow not doing enough," a senior U.S. official said on condition of anonymity. "I do think it's fair to say that there are divisions in those ranks."
Washington says the weapons flow from Russia increased dramatically several weeks ago in response to the government forces' successes.
The army's latest advances in eastern Ukraine have come since a Malaysian airliner was brought down on July 17 in rebel-held territory, killing all 298 people on board.
Moscow says Kiev's military campaign was to blame for the crash. The United States says the rebels probably shot the plane down by mistake with a Russian-made SA-11 ground-to-air missile. (Additional reporting by Phil Stewart, writing by Gabriela Baczynska, editing by Timothy Heritage and Will Waterman)