(Repeats Sunday item)
* Assad trying for months to dislodge rebels from the suburbs hit
* Rebels dug in and well organised in Ghouta and Mouadamiya
* Developments in recent weeks increased rebel threat to Damascus centre
By Khaled Yacoub Oweis
AMMAN, Aug 26 (Reuters) - A diplomat and activists said Syrian President Bashar al-Assad had been trying for some time, in vain, to dislodge rebels from the areas not far from central Damascus that were hit by suspected chemical weapons last week.
Assad has strongly denied carrying out chemical attacks, telling Russian newspaper Izvestia on Monday that the allegation "insults common sense" and that the rebels were responsible for what could be the world's worst poison gas strike in 25 years.
Even some locals in rebel-held areas hit by the strike have questioned the rationale for such an attack so close to Assad's own forces and just a few days after UN weapons inspectors arrived in the city to investigate previous allegations of chemical weapon use.
The hundreds of deaths caused by the Aug. 21 attacks have also drawn threats of military retaliation from Western powers, which could turn the tide against Assad's efforts to defeat a 2-1/2-year revolt against his rule.
But diplomats and rebels interviewed by Reuters said Assad's generals had been trying for some time to push the rebel units back to the southern ring road that separates Damascus from its more rural environs and neutralise the immediate threat to the heart of the capital.
The suburbs of Zamalka, Jobar and Ain Tarma sit in an expanse of farming country known as the Eastern Ghouta. Along with the town of Mouadmiya in the west, these areas had been pummelled for months by battlefield artillery, warplanes and surface-to-surface missiles before they were hit on the morning of Aug. 21.
In the 72 hours that followed, Assad's mechanised forces from the Fourth Division and the Republican Guards, the praetorian units entrusted with defending his seat of power, mounted a major push to retake the four areas, but well dug-in rebels held out, sources said.
"The regime has been throwing everything he has at the Ghouta, but it remained a thorn in its side. When you have a large number of well-organised rebel fighters in an urban area with lots of cover, using chemical weapons becomes very tempting," a Middle East based diplomat said.
When the revolt became militarised almost two year ago, the rebels of Ghouta, mostly from the Sunni majority that opposes Assad and his minority Alawite sect elite, were among the first areas in the country to take up arms.
The rebel groups there include the Saudi-backed Liwa al-Islam Brigade, Saladin Brigade, Jobar Martyrs Brigade, and Tahrir al-Sham, a unit headed by Firas al-Bitar, an officer who defected from Assad's army and has a reputation as a good military planner.
"If the rebel units were not so well organised, Assad would have captured Ghouta long time ago," said Moaz al-Shami, a prominent activist who witnessed fighting in Ghouta.
"The regime needed to kill 1,000 people in one go in Ghouta, or whatever the final tally of the chemical attack proves to be, because it was in need of a morale boost," he added.
In the last few weeks, rebel brigades based in Jobar, which is only three kilometres from the central Abbassiyeen Square, managed to open a supply corridor to the besieged Damascus neighbourhoods of Barzeh and Qaboun in the northern sector of the capital, opposition sources said.
The link brought the military threat from Ghouta closer to the heart of Damascus and helped the two districts withstand intensifying loyalist attacks, the sources said.
"Rebel operations in the countryside have been merging with Damascus, and the regime could not take that. Assad would have loved to gas Barzeh and Qaboun as well, but they are too interconnected with loyalist areas," said Khaled Omar, a member of the opposition Local Council of Ain Tarma.
"By hitting Ghouta, Assad thinks he is preserving Damascus and destroying a popular incubator of the revolution," he added.
To the West, in Mouadamiya, activists said at least 80 people were killed when the district was hit with nerve gas an hour after the attack on Irbin, Ain Tarma and Jobar.
Over the past four decades, Syrian authorities have confiscated much of Mouadamiya to expand the Mezze military airport and compounds for the Republican Guards and Fourth Division, which now surround the town.
Most of Mouadamiya's residents had already fled after Assad's forces had overrun the suburb several times in the last year. About 9,000 civilians have remained in the district, according to opposition activist Wassim al-Ahmad.
"The regime attacked Mouadamiya with chemical weapons because it is strategic, and because after nine months of siege, it found no other way," he said. (Editing by Will Waterman)