The Commander of U.S. Central Command Gen. James Mattis and Pakistan's top military leaders have held "candid discussions about the current challenges in the U.S.-Pakistan relationship", the U.S. embassy said in Islamabad Sunday.

Mattis' two-day visit (Friday and Saturday) to Pakistan came after ties between Pakistan and the U.S. was strained after top U. S. defenec officials accused Pakistan's intelligence agency of supporting the Haqqani network blamed for recent attacks on the U. S. embassy and a military base in Afghanistan.

The U.S. urged Islamabad to take strong action against the Haqqani network which operates from Pakistan's North Waziristan tribal region bordering Afghanistan. Pakistan denies it has any links with the Haqqani network.

Mattis met with Gen. Ashfaq Kayani, the Chief of Pakistan Army, and Gen. Khalid Wynne, the Chief of Staff of Pakistan Armed Forces.

"Gen. Mattis meets and talks routinely with both generals to discuss U.S.-Pakistan military activities, the coalition campaign in Afghanistan and broader regional issues," the U.S. embassy statement said.

"However, Gen. Mattis also emphasized the vital role the Pakistan military plays in international security efforts to protect the Pakistani and Afghan people and the need for persistent engagement among the militaries of the U.S., Pakistan and other states in the region," the statement said.

General Kayani said the U.S. accusation was disturbing cooperation between the U.S. and Pakistan, and demanded the U.S. troops halt attacks on Pakistani border posts by militants from Afghan territory, according to local media.

U.S. Defence Secretary Panetta last week threatened to take unilateral action against Haqqani network if Pakistan failed to target the militants on its soil.