Islamabad: U.S. National Security Adviser Susan Rice met Pakistan's prime minister on Sunday to press concerns over attacks launched by militants based in Pakistan, officials said.

The visit to Islamabad, part of an Asian tour that included an earlier stop in China, comes amid uncertainty over whether the United States will release $300 million in military aid to Pakistan.

Media reports have suggested the money could be held back if the United States determines Pakistan is not doing enough to combat the Haqqani network, which has launched some of the deadliest attacks in neighbouring Afghanistan.

Rice "will address areas of mutual interest and of concern, including terrorist and militant attacks emanating from Pakistani soil", a senior U.S. official who asked not to be identified.

The official said Rice's visit was not in response to recent escalating tension between Pakistan and arch-rival India, who cancelled planned peace talks last weekend. Nine people were killed during an exchange of fire on Friday along a border disputed by India and Pakistan.

The United States has urged Pakistan and India to get reconciliation talks back on track.

Rice met Pakistani Prime Minister Nawaz Sharif on Sunday and was expected to meet General Raheel Sharif, the army chief of staff, later in the day.

"Dr. Rice expressed deep appreciation for the sacrifices made by Pakistan in the efforts to root out terrorism and extremism and the success achieved so far," a statement from Sharif's office said.

Pakistan's military has been waging a fierce offensive against the Pakistani Taliban and its radical Islamist allies in North Waziristan, near the Afghan border, since last year.

Some have questioned whether the leadership of the Haqqani network, which is allied with but separate to the Taliban, had been allowed to leave to avoid the brunt of the assault.

The United States is also keen to gain Pakistan's help in resurrecting peace talks between the Afghan Taliban and the government in Kabul.

The tentative process toward negotiating an end to almost 14 years of war in Afghanistan was thrown into disarray last month with the revelation that long-time Taliban leader Mullah Mohammad Omar had been dead for two years.