BOGOTA, Colombia (AP) - Rebel attacks that have killed almost 50 soldiers in less than two weeks have shaken confidence in government claims it finally has the upper hand against leftist insurgents after 40 years of warfare.

The government insists the Revolutionary Armed Forces of Colombia, or FARC, are simply taking advantage of chinks in the military's shield of protection and of overconfidence of government forces in this Andean nation.

The rebels began the latest spate of attacks on Feb. 1 by firing rockets into a military post in the southwest, killing 16 marines and injuring 25.

A day later, in south-central Colombia, eight soldiers died when their vehicle was hit by rebel explosives. The bloodiest attack was in northwest Colombia on Tuesday and Wednesday, when rebels killed 19 soldiers in a firefight.

Since President Alvaro Uribe launched an offensive called Plan Patriot a year ago against the FARC's southeastern jungle strongholds, the rebels have been in a tactical retreat, experts say. They have melted into the jungle ahead of advancing government troops and been hesitant to engage them directly anywhere in the nation.

All that changed with the rebel attacks this month, said Alfredo Rangel, an analyst and former adviser to the Defense Ministry.

"It is the beginning of the end of the FARC's retreat," Rangel said, adding that the rebels aim to change the perception that the country is safe from their attacks, especially as Uribe - a hard-liner who has vowed to bring them to their knees - prepares to run for re-election in 2006.

Carlos Lozano, managing editor of Colombia's Communist Party newspaper, said the attacks show the FARC, which has been fighting the government for 40 years, "is used to adapting to new circumstances (and) remains intact."

Sen. Rafael Pardo, a former defense minister, said the military's setbacks this month do not take away from the Uribe administration's successes in fighting the rebels. Kidnappings - a source of income for the guerrillas - fell to 1,441 last year, a 35 percent drop from the previous year. Terrorist attacks declined 44 percent to 709 and homicides fell 15 percent.

As a result, tourism is surging, the economy is growing, foreign investment is rising and the Colombian peso is at its strongest level against the dollar in years.

"You have to measure the security policy by what it has achieved, not the problems of the past few days," Pardo said.