The Taliban have stepped up their attacks in Pakistan in recent weeks
Pakistan's army chief has said the head of the Taliban in Pakistan "must be eliminated".
General Ashfaq Kayani said Baitullah Mehsud, who has his stronghold in the tribal district of South Waziristan, was "not fighting for Islam".
His comments come as a provincial governor said an offensive to target militants was imminent. Neither man said when such an assault might begin.
Baitullah Mehsud's group is blamed for a string of deadly attacks in Pakistan.
Last week a prominent Muslim cleric who was outspoken in his opposition to the Taliban was killed in a suicide blast at his seminary in Lahore.
Gen Kayani said that militants targeted children, the elderly and clerics - and as such they were Pakistan's enemies.
"We are conducting this operation to bring misguided people back on the right path," he said.
"They are not fighting for Islam. Pakistan was created in the name of Islam and we know how to protect it," he added.
Correspondents say the announcement of any operation is likely to please the US.
Washington regards the tribal region as a particularly troublesome hideout for al-Qaeda and Taliban fighters suspected of attacks on US forces in neighbouring Afghanistan.
The BBC's M Ilyas Khan in Islamabad says Baitullah Mehsud is thought to head the most powerful group of militants in the country, with a network of alliances with other militants in the Orakzai, Bajaur and Malakand regions.
His stronghold in South Waziristan, bordering Afghanistan, is an area rumoured to be the hideout of Osama Bin Laden.
Gen Kayani, speaking at a ceremony, did not explicitly confirm that the Pakistani army had gone after Baitullah Mehsud yet.
He later boarded an F-16 fighter jet to carry out an attack as part of the broader operation against the Taliban - a symbolic gesture as Gen Kayani is not a pilot.
His comments come a day after North West Frontier Province governor Owais Ahmad Ghani said troops had been ordered to target militants in the area.
"The Pakistan army and other law-enforcing agencies have been directed to crush the militants through a full-fledged and comprehensive plan," Mr Ghani told reporters in Islamabad.
Analysts in Pakistan have been puzzled over why the offensive has been publicised before being launched, removing any element of surprise.
Many point out that an operation against Baitullah Mehsud will require consensus across Pakistan's political spectrum, which only the central government can develop.
In the past, Pakistani army action has faltered or ended in truces that correspondents say have strengthened the militants.
Gen Kayani acknowledged the difficulties of the challenge. He said the war they were fighting was not a conventional war and that it was very difficult to discriminate between a friend and a foe.
Analysts say that in many ways a full-scale operation in South Waziristan would be harder than the recent fighting in the Swat valley, where Pakistani troops say they killed hundreds of militants in the past six weeks.
So far the armed forces have described their operations in South Waziristan as limited, compared with the high-profile offensive in the Swat valley further north.
Meanwhile, militants have been targeting sites across north-west Pakistan.
At least eight people were killed in a bomb attack at a market in the north-western town of Dera Ismail Khan on Sunday.
The explosives were reported to have been detonated by remote control after being hidden in a rickshaw.
The authorities blamed the attack on supporters of Baitullah Mehsud.
A spokesman for Baitullah Mehsud has claimed that his group, Tehreek-e-Taliban Pakistan, has also been behind several other deadly attacks on Pakistani civilians recently, AFP news agency reported.
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