It is just a matter of time before the government of Syrian President Bashar al-Assad falls because its use of massive force is mobilizing insurgents, General Robert Mood, the former head of the UN monitoring mission in Syria, said on Friday, according to Huffington Post.

"In my opinion it is only a matter of time before a regime that is using such heavy military power and disproportional violence against the civilian population is going to fall," the Norwegian general, who left Damascus on July 19, told Reuters.

"Every time there are 15 people killed in a village, 500 additional sympathizers are mobilized, roughly 100 of whom are fighters," Mood said.

However, the authoritarian Syrian leader is probably secure in the short term because he has the military capability to hold off the rebels and his eventual fall could be months or even years away, Mood said.

"In the short term it may very well be possible for him to (hold on), because the military capabilities of the Syrian army are much much stronger than those of the opposition," Mood said.

"The minute you see larger military formations leaving the ranks of the government to join the opposition, then that is when it starts accelerating ... This could last for months or even years," he said.