US Secretary of State Rex Tillerson landed in Islamabad Tuesday as Washington turns up the heat on Pakistan for allegedy providing "safe havens" for Taliban militants.

Tillerson's visit, his first to Pakistan since becoming secretary of state, comes months after US President Donald Trump angrily accused the nuclear-armed country of harbouring "agents of chaos" who can attack NATO-led forces in neighbouring Afghanistan.

It follows on the heels of an unannounced stop in Afghanistan, where the US top diplomat reiterated America's commitment to the country and warned Washington has made "very specific requests" of Pakistan seeking to "undermine the support that the Taliban receives".

Washington and Kabul have long accused Islamabad of supporting militant groups including the Taliban, believed to have links to Pakistan's shadowy military establishment who aim to use them as a regional bulwark against arch-nemesis India.

Pakistan has repeatedly denied the charge, insisting it maintains contacts only with the militants as it seeks to bring them to the table for peace talks.

During his brief trip to Bagram air base Monday, Tillerson told reporters Pakistan needs to "take a clear-eyed view of the situation that they are confronted with in terms of the number of terrorist organisations that find safe haven inside" the country.

His visit to Islamabad, where he is meeting with Prime Minister Shahid Khaqan Abbasi and the powerful military chief General Qamar Javed Bajwa, marks the first by a member of the administration.

US and Pakistani sources say he will be followed later in the year by Defense Secretary Jim Mattis as Trump seeks to send a tough message to the wayward ally.

The US-Pakistan relationship has waxed and waned dramatically since Trump took office in January.

Pakistan said the President had praised its then-prime minister Nawaz Sharif as "terrific" in an effusive phone call when Trump took office in January.

But Trump's blistering speech in August accusing Pakistan of harbouring militants saw Islamabad angrily hit back at the claims, insisting they discount the thousands of lives lost and billions spent in fighting extremism.

Following the speech, Tillerson cautioned Pakistan that it could lose its status as a privileged military ally if it continued providing support to Afghan militant groups.

As one of 16 "Non-NATO Major Allies", Pakistan benefits from billions of dollars in aid and has access to advanced US military technology banned from other countries.

Earlier this month Pakistani forces acting on American intelligence rescued a US-Canadian family that had been in Taliban captivity for five years, sparking hopes that ties were on the mend.

The rescue was followed by a series of drone strikes on both sides of the Afghanistan-Pakistan border targeting long-time foes to both Washington and Islamabad.

The US has vowed to send more than 3,000 additional troops to Afghanistan, on top of the 11,000 already deployed there, to train and advise Afghan security forces as part of a new strategy outlined by the administration.

Source: AFP