ACHIN, Afghanistan -- American and Afghan officials have begun helping a number of anti-Taliban militias that have independently taken up arms against insurgents in several parts of Afghanistan, prompting hopes of a large-scale tribal rebellion against the Taliban.

The emergence of the militias, which took some leaders in Kabul by surprise, has so encouraged the American and Afghan officials that they are planning to spur the growth of similar armed groups across the Taliban heartland in the southern and eastern parts of the country.

The American and Afghan officials say they are hoping the plan, called the Community Defense Initiative, will bring together thousands of gunmen to protect their neighborhoods from Taliban insurgents. Already there are hundreds of Afghans who are acting on their own against the Taliban, officials say.

The endeavor represents one of the most ambitious -- and one of the riskiest -- plans for regaining the initiative against the Taliban, who are fighting more vigorously than at any time since 2001.