The tough message was conveyed by Admiral Mike Mullen, Chairman of the Joint Chiefs of Staff, to his Pakistani counterpart Kayani at a two-hour private meeting late Friday during a military conference in Seville, Spain, where the two discussed their nations` complicated relationship.
Mullen has expressed "deep concerns" about violent attacks mounted by the Haqqani network, his spokesman said.
The US has again pressed the Pakistani military to take action against militant havens, he said.
"Admiral Mullen conveyed his deep concerns about the increasing -- and increasingly brazen -- activities of the Haqqani network and restated his strong desire to see the Pakistani military take action against them and their safe havens in North Waziristan," Capt John Kirby, Special Assistant for Public Affairs, Chairman of the Joint Chiefs of Staff said.
"They agreed that the relationship between our two countries remained vital to the region and that both sides had taken positive steps to improve that relationship over the past few months," Kirby said.
They also discussed the state of military-to-military cooperation and pledged to continue to find ways to make it better, Kirby said.
Relations with Pakistan have not recovered from a near-rupture after the killing of Osama bin Laden by American commandos operating deep inside Pakistan in early May.
In recent days, American military officials said that a brazen attack on the United States Embassy compound and NATO headquarters in Kabul bore the hallmarks of the Haqqani network, a militant group based in Pakistan.
American officials have said they have compelling evidence that Haqqani fighters have received support and direction from Pakistan`s intelligence agency, the Inter-Services Intelligence Directorate.