PESHAWAR, Pakistan - The path to terrorist training in Pakistan is well-worn, developed and maintained by established militant groups that have operated for decades. They are open to those - Americans included - with enough determination and savvy to navigate the extremist networks and the dangerous borderlands.

U.S. prosecutors allege Faisal Shahzad, the Pakistani American charged in the failed Times Square bombing, is among those who have made the journey. Officials say five young American Muslims tried to link up with extremists with less success: They now face trial in Pakistan.

The numbers of would-be jihadis are dropping because Pakistani military operations and two years of U.S. drone air strikes have made Somalia and Yemen more attractive destinations, said Mahmood Shah, a retired brigadier and the military's former point man in the tribal regions.

But analysts and Pakistani officials say it is surprisingly easy for would-be jihadists, including foreigners, to reach training facilities in the border area.

Would-be jihadis, many recruited abroad by al-Qaeda, enter Pakistan through either the northwest city of Peshawar or the southern port city of Karachi. From there they make their way through safe houses to the border area, according to Pakistani intelligence and security officials.

Training takes place in makeshift camps that move about to avoid detection by U.S. drones, which have killed as many as 300 people this year, according to the New America Foundation, which keeps a database of attacks. Human-rights groups say many of the dead have been civilians, fueling anti-Americanism among Pakistan's 175 million people and possibly encouraging young Muslims to join the jihad.

A Pakistani intelligence official involved in the investigation of Shahzad's activities in Pakistan said al-Qaeda operatives arranged recruits' trips to Pakistan and provided a local contact to take them from the airport to the network of safe houses, usually in congested neighborhoods.

Once in the country, foreigners of Pakistani origin such as Shahzad can move freely, especially if they hold dual citizenship. They are not routinely shadowed by the intelligence service unless their names are on an international watch list, officials said.

Trainees travel to and from the camps with escorts who often are strangers to one another so that if one is arrested, the network is not compromised, the official said on condition of anonymity because he's not supposed to release information.

Training lasts about 20 days, said the brother of a militant who attended a camp in North Waziristan. Lectures on the philosophy of jihad are usually delivered by foreigners, mostly Arabs, he said, speaking on condition of anonymity for his safety.

The network relies on numerous militant organizations that have existed in Pakistan for decades, such as Sipah-e-Sahaba, Jaish-e-Mohammed, and Lashkar-e-Janghvi.

For security and logistics, the network also looks to private religious schools, or madrassas, and mosques with links to extremist groups. Some foreign militants enter the country on visas to study at a madrassa. Others are helped by students or staff, who can provide places to stay and help with transport in the country.

Former Pakistani President Pervez Musharraf promised years ago to curb the madrassas and regulate their curriculums to eliminate Islamic extremist teachings. Those efforts fell short because of the political power of the religious establishment in a country where madrassas are often the only source of education for the nation's poor.

The proliferation of militant groups - some banned but operating under new names - featured prominently in recent talks in Islamabad between Pakistani officials and CIA Director Leon Panetta and National Security Adviser James Jones, according to Pakistani officials close to the talks who spoke on condition of anonymity because the talks were private.