Islamabad: The US military`s top officer arrived in Islamabad on Saturday amid US concerns over the presence in Pakistan of Islamist militants blamed for attacks on NATO-led troops in Afghanistan.
Admiral Mike Mullen planned to meet US officers overseeing military assistance to Pakistan, before meeting the country`s powerful Army chief, General Ashfaq Kayani, whose term was extended by three years on Thursday.
Mullen and US officials have praised Pakistan for moving against militants in the northwest but have urged the military to expand its operations to include the Haqqani network.
On the eve of his one-day visit, Mullen acknowledged US worries over extremist sanctuaries in Pakistan, including the Haqqani network based in North Waziristan.
Speaking at news conference in New Delhi, Mullen called the Haqqani militants "the most lethal network" faced by the US-led international force in Afghanistan and said he had repeatedly urged Pakistan to tackle the threat.
"I continue to address that with the (Pakistani) leadership as a very, very strong priority," Mullen told reporters at the end of a two-day visit to India.
Kayani "is aware of that priority and in terms of what we think needs to happen," Mullen said.
Created by Afghan warlord Jalaluddin Haqqani and run by his son Sirajuddin, the Haqqani group is one of the toughest foes for foreign forces in Afghanistan, particularly in the east of the country.
Mullen also said Pakistan`s intelligence service needed to change its outlook, an apparent reference to charges that Pakistan`s intelligence agency ISI sees Islamist militants as a hedge against its arch-rival India.
"I believe the strategic approach, the overall strategic approach of ISI, needs to fundamentally change," he said.
Mullen was due to take an aerial tour at an unspecified location in the north, where Kayani planned to brief him on Pakistani operations against Taliban militants, US officers said.
Prime Minister Yousuf Raza Gilani announced on Thursday he had extended Kayani`s term for three years, a move welcomed by US officials who credit the general for launching offensives against Taliban militants last year.
Mullen, chairman of the Joint Chiefs of Staff, has gone out of his way to cultivate Kayani and aides said Saturday`s trip was the admiral`s 19th visit to see the Pakistani general.
Kayani assumed command of the Pakistan army in November 2007 after his predecessor, Pervez Musharraf, relinquished command amid international pressure to end his eight years of military rule.
Arguably the most powerful man in nuclear-armed Pakistan, Kayani is a pivotal figure for the Obama administration as it seeks to contain Islamist insurgents fighting the Kabul government and Islamabad`s authority.
Washington calls the tribal belt on Pakistan`s western border the global headquarters of the al Qaeda terror network and the most dangerous place on Earth.
Mullen`s visit coincided with another apparent US drone strike in Pakistan, with unmanned aircraft firing four missiles into a compound used by Islamist fighters in the northwestern tribal belt.
At least 11 militants were killed in the attack, security officials said.