US Defense Secretary Chuck Hagel discussed the use of drones against militants in remote areas of Pakistan on Monday during the first visit by a Pentagon chief to the South Asian ally in almost four years.

The US has a complicated relationship with Pakistan and ties have been further soured by a dispute over unmanned military aircraft the US uses to target militants in Pakistan's tribal areas on the Afghan border.

Islamabad says drone strikes kill too many civilians and violate its sovereignty. Protests by anti-drone activists prompted the US to suspend ground shipments of NATO cargo leaving Afghanistan via Pakistan last week.

During his visit, Hagel met Prime Minister Nawaz Sharif and other senior officials including the newly appointed army chief, Raheel Sharif. Both sides were tight-lipped on the details of the talks.

"The prime minister ... conveyed Pakistan's deep concern over continuing US drone strikes, stressing that drone strikes were counter-productive to our efforts to combat terrorism and extremism on an enduring basis," the Pakistan's foreign ministry said in a statement.

Before his arrival in Pakistan, Hagel visited troops in Afghanistan and met senior Afghan officials. He said a NATO meeting in February could serve as a new deadline for approval of a security pact between Kabul and Washington - an accord Afghan President Hamid Karzai has been reluctant to sign.

Hagel is the first defense minister to visit Pakistan since the US raid in the city of Abbottabad that killed Al Qaeda leader Osama bin Laden in 2011. Pakistan was embarrassed and angered by the surprise raid.

At the same time, Pakistan has served as a supply route for equipment flowing into Afghanistan to support the international coalition that is fighting Taliban militants.

The routes, known as the Pakistani Ground Lines of Communication (GLOC), are important for withdrawing US and coalition equipment as they draw down foreign forces in Afghanistan and hand over security control to Afghan security forces.

Prior to the talks, a US defense official said Hagel would "express appreciation that ... the government of Pakistan has made it a priority to keep the GLOC open."

Reuters