PESHAWAR, Pakistan — As Pakistani forces press ahead with their most concerted campaign in years against Taliban and Al Qaeda fighters in the dry, jagged hills of Pakistan’s tribal belt, the insurgents have moved to establish new footholds in remote corners of the Texas-sized region along the border with Afghanistan.

The Islamic militants are seeking to spread their influence in areas previously untouched by fighting, and are in some cases forging new alliances between outside groups and local insurgents, observers and officials say. The insurgents are also increasingly employing heavy weapons, and they have made several brazen frontal attacks on army outposts that differed significantly from hit-and-run guerrilla-style skirmishes of the recent past.

“They’ve become better organized, more disciplined and more capable of mounting big attacks,” said Rahimullah Yusufzai, an analyst based here in Peshawar, capital of Pakistan’s North-West Frontier Province, which abuts the tribal belt.

The outcome of the Pakistani offensive will probably affect not only the course of the war in Afghanistan, where cross-border infiltration poses a serious threat to American and NATO troops, but also American relations with Pakistan, a key ally. President Musharraf, an army general who seized power eight years ago and is now beset by domestic political woes, has staked much of his remaining prestige on successfully confronting the insurgents.

On Sunday, General Musharraf acknowledged that Islamic militants operate in his nation’s tribal areas, where they provide support to fighters in Afghanistan. The unusually candid admission came at the end of a four-day tribal meeting in Kabul.

Last week, General Musharraf hinted that he might use the fighting as a justification for imposing a nationwide state of emergency — a move that would give him broad powers that could be wielded against a growing pro-democracy movement. The general backed down after a storm of objection from both the international community and broad swaths of Pakistani society, but aides said the option was still open.

The violence has been centered in North Waziristan, the most volatile of the seven Pushtun tribal areas that are described as “federally administered” but are beyond the writ of Pakistan’s central government. Often fierce clashes between Pakistani government forces and militants, coupled with suicide attacks around the country, have killed more than 250 people in the last month. The fighting began in earnest after a ninth-month-old truce between Taliban-backed tribal elders and Pakistan’s military broke down last month.