Dera Ismail Khan, Pakistan ? Pakistani troops and the Taliban fought fierce battles in a militant sanctuary near the Afghan border, with both sides claiming early victories in an army campaign that could shape the future of the country’s battle against extremism.

The offensive in South Waziristan was expected to be a key topic of discussion today as U.S. Sen. John Kerry and U.S. Central Command chief David Petraeus visited Pakistan for talks with military and political leaders. American officials have pushed Pakistan to crack down on extremists who use its soil as a base for planning attacks on Western troops in Afghanistan.

A Taliban spokesman vowed the Islamist militants would fight to “our last drop of blood” to defend their stronghold in South Waziristan, predicting the army would fail in its latest attempt to gain control over the tribal region.

The army said Sunday that 60 militants and six soldiers had been killed since the offensive began Saturday in the mountainous, remote region that the army has tried and failed to wrest from near-total insurgent control three times since 2004.

The Taliban claimed to have inflicted “heavy casualties” and pushed advancing soldiers back into their bases. It was not possible to independently verify the claims because the army is blocking access to the battlefield and surrounding towns.

Victory for the government in South Waziristan’s tribal badlands would eliminate a safe haven for the Taliban militants blamed for surging terrorist attacks and the al-Qaida operatives they shelter there. It would also send a signal to other insurgent groups in the nuclear-armed country of the military’s will and ability to fight them.

Defeat would give the militants a propaganda victory, add to pressures on the country’s shaky civilian government and alarm Pakistan’s Western allies.

“We know how to fight this war and defeat the enemy with the minimum loss of our men,” Taliban spokesman Azam Tariq told The Associated Press from an undisclosed location. “This is a war imposed on us, and we will defend our land until our last man and our last drop of blood. This is a war bound to end in the defeat of the Pakistan army.”

Despite his comments, the some 10,000 Pakistani militants and about 1,500 foreign fighters are seen as unlikely to stand and fight. Instead, they will likely do as they have done in other parts of the northwest: Avoid conventional battles and launch guerrilla attacks on stationary troops or long supply lines.

Accounts from residents and those fleeing Sunday suggested that the some 30,000 government troops pushing into the region from three directions were facing much tougher resistance than they saw in the Swat Valley, another northwestern region where the army defeated the insurgents earlier this year.

“Militants are offering very tough resistance to any movement of troops,” Ehsan Mahsud, a resident of Makeen, a town in the region, told the AP in the town of Mir Ali, close to the battle zone. He and a friend arrived there early Sunday after traveling through the night.

Mahsud said the army appeared to be mostly relying on airstrikes and artillery against militants occupying high ground. He said the insurgents were firing heavy machine guns at helicopter gunships, forcing the air force to use higher-flying jets.

The militants control roughly 1,275 square miles of territory, or about half of South Waziristan, in areas loyal to former militant chief Baitullah Mehsud, who was killed in a U.S. missile strike in August. His clansman Hakimullah Mehsud now leads the Tehrik-e-Taliban Pakistan, or Pakistani Taliban Movement, an umbrella organization of several Islamist militant factions seeking to overthrow the secular government.

Officials have said they expect the operation will last two months, when winter weather will make fighting difficult.