The road to Tripoli will almost certainly be bloody, admit the leaders of Libya's rebel army

Colonel Hamid Belkhair sat behind a desk in the sparse room that makes for a rebel command centre and spoke with grim certainty about the coming battle.

"I swear by God he has been preparing for this for a very long time," he said of the dictator who less than two weeks ago he had deferred to as commander-in-chief. "I am 1,000% sure it is impossible to get to him without a fight. He is a very bad person."

The past few days have been a time of reckoning for the tired band of revolutionaries that comprise Libya's rebel army. After a flush of euphoria, they face the realisation that the road to Tripoli will almost certainly be bloody.

The rebels have spent this week tallying the weapons they seized from the government. "The arms he has are far more than the arms he left behind," Belkhair said. A stark reality is emerging – they could not hold out for long against the dictator's forces if he attacked. Foreign help may be needed to finish what they started.

"He has been recruiting from Africa and he is massing a big army of mercenaries to the south," said Belkhair, slouching forward on a three-legged chair in a base in central Benghazi. "His aim is to cut our supplies and bomb all our weapons. He will use those mercenaries to attack us."

On Monday, two fighter jets from Tripoli bombed the city of Ajdabiya, 100 miles south of Benghazi, the farthest east Gaddafi's forces had reached since their ignominious retreat on 20 February. The jets appeared to have targeted military armouries in which artillery shells and ammunition had been left.

"We had several anti-aircraft positions, which fired at the planes," said Belkhair. "Then they fled. They were not interested in hanging around."

Pro-government forces were reported to have returned to the oil town of Ras Lusafa, about 125 miles further west, which had been the last rebel safe haven before the Gaddafi stronghold of Sirte, roughly halfway to Tripoli.

The rebels are certain that the coming days will bring more attacks, as well as attempts to unsettle residents by disrupting civic services such as water and electricity. An anti-aircraft position was established on Benghazi's waterfront to shore up the city's defences, but it was later repositioned.

The rebel military has no anti-aircraft missiles and only a small number of old jets that they fear would be no match for the predominantly Russian-made MIGs flown by the remnants of the air force.

Inside the base, a group of rebel soldiers still wearing Libyan army uniforms were greasing and oiling large calibre rounds to fire at attacking jets from rudimentary anti-aircraft guns fixed to the back of utility trucks. Others were loading ammunition into lorries.

Were they going to the front line? "God willing," came the reply.

A second officer, Major Ibrahim Agouri, spoke up. "We are the remnants of the traditional army, the public army. All of us (in Benghazi) defected as soon as this revolution started. His special security forces went with him. They are all for his own protection and they have no problem killing their own people."

The base was almost the town's only government building not burned and ransacked. There had been some foresight even during the rampant pillaging. But rebel commanders acknowledge that much more is needed as Gaddafi loyalists try to claw back their losses.

"There will be a final decisive fight," said Agouri. "And we cannot afford to lose it or he will kill us all."

One option that rebel leaders are now being forced to consider is to accept international help to oust Gaddafi. Such a move could potentially jeopardise their claim to have launched the revolution with nationalistic aims and add weight to the regime's claims that they are fighting a foreign-led coup.

"We can accept supplies," said Belkhair. "We don't need soldiers."

Then came what was almost a request to take care of the rebels' worst fears. "We would welcome air force support and any equipment. If we can take hold of Sabah air base (in southern Libya), we can stop the mercenaries coming in and this would be a savage blow to his offensive options. He is only still in power because of his air force."

On Monday night, residents in Benghazi were taking some comfort from discussions in the US and Europe about enforcing a no-fly zone. For now, the menace from the sky appears very real. Bombardment is no stranger to this coastal city, which was levelled during the second world war by attacks from allied and axis forces, neither of which could hold it.

But the coming threat is different. "He killed the city's children last weekend and he will do it again. A Libyan leader attacking his own people is a terrifying thought."

As the sun set, the rebels were perched behind the few anti-aircraft guns they hold, their thin turrets pointing towards an empty black sky. The streets were as empty as they have been in a week.