The Pakistani Taliban's appointment of a new hardline leader opposed to peace talks and with a long history of attacks against the military could push the army into launching a fresh offensive, analysts said Friday.
The election of Maulana Fazlullah, notorious for leading the militants' brutal two-year rule in Pakistan's northwestern Swat valley, is like a "red rag to a bull", one analyst said.
It could also raise tensions with Kabul at a critical juncture as US-led forces withdraw from Afghanistan after 12 years of war.
While Kabul has long accused Islamabad of supporting the Afghan Taliban, Fazlullah has orchestrated cross-border attacks from his hideout in eastern Afghanistan, and Pakistan suspects its neighbour's intelligence services of supporting him.
Fazlullah, nicknamed Mullah Radio for his fiery sermons over the airwaves denouncing polio vaccination campaigns and female education, is renowned as an uncompromising commander.
Pakistani intelligence believes he is linked to the failed attempt to kill schoolgirl education activist Malala Yousafzai, who was shot in Swat in October 2012. He was appointed chief of the Tehreek-e-Taliban Pakistan (TTP) on Thursday, nearly a week after a US drone strike killed his predecessor Hakimullah Mehsud.
Islamabad reacted angrily to the killing of Mehsud, with the interior minister saying Washington had "sabotaged" peace talks.
It is not clear what progress, if any, had been made towards meaningful dialogue -- but the process lies in tatters after Fazlullah's election.
On Thursday, the militants dismissed the idea of peace talks with the government as a "waste of time", and said they would never negotiate until sharia law was imposed across the country.
Defence analyst Talat Masood, a retired general, said the TTP's choice of Fazlullah, whose men have carried out bloody and humiliating attacks against the army, was like a "red rag to a bull".
"This leaves no margin for negotiation and they will have to resort to a military operation and will have to be fully prepared to prevent terrorist actions in the country," Masood told AFP.
"He is enemy number one of the military."
In September, political parties backed the government's proposal for talks to try to end the TTP's six-year insurgency, which has killed thousands.
Fazlullah's men responded by killing two senior army officers, including a major general, in a roadside bomb -- a galling blow to the pride of the military, which remains the most powerful institution in Pakistan.
Fazlullah rubbed salt in the wounds by issuing a video message to claim the attack and to reveal the intended target was General Ashfaq Kayani, the army's supreme commander.
In 2009 a major military operation ended Fazlullah's rule in Swat. Later that year another offensive cleared militant hideouts in South Waziristan, one of the seven tribal areas along the Afghan border seen as a haven for Taliban and Al-Qaeda militants.
Washington has pushed for a similar offensive in North Waziristan, which has borne the brunt of the US drone campaign targeting suspected militants, but none has yet taken place.
A senior security source told AFP a military operation would "become inevitable" if, as seems likely, dialogue does not proceed, and warned of worsening relations with Kabul.
"The government and the military top brass in almost all previous rounds of meetings with their Afghan interlocutors have been pointing out Fazlullah's presence on Afghan soil and his activities against the Pakistani state," the source said.
Kayani is to retire on November 29 and his replacement as army chief has yet to be announced. The security official said Fazlullah's appointment would have a bearing on the decision.
"The priority will now be to have a person on this post, who has expertise in counter insurgency and related matters," the official said.