U.S. Defense Secretary Leon Panetta warned Pakistan Wednesday that the United States would "do everything we can" to defend against Pakistan-based militants attacking in Afghanistan.
Panetta's comments follow U.S. officials assigning blame to the Haqqani network - based in Pakistan's North Waziristan tribal region - for Tuesday's 20-hour assault on the Afghan capital Kabul. In the attack, militants targeted the U.S. Embassy, NATO headquarters and other high-profile targets using rocket-propelled grenades, gunfire and suicide bombings.
NATO officials said 11 Afghan civilians, more than half of them children, were killed, along with five Afghan police officers. More than two dozen people also were wounded, including six NATO troops. No embassy staff members were hurt.
Speaking to reporters aboard his military aircraft, Panetta said it is "unacceptable" that militants are able to launch deadly attacks in Afghanistan and then flee to safe havens across the border in Pakistan.
Panetta said Washington repeatedly has urged Islamabad to "exercise its influence" to prevent such actions. He added that the United States would not allow such raids to continue, but he refused to elaborate.
The Reuters news agency quoted a spokeswoman for Pakistan's foreign ministry as saying Panetta's remarks were not in line with the counter-terrorism cooperation between the two nations.
Senior Pakistani officials also told Reuters that it was the responsibility of the Afghan government and international coalition to stop militants when they enter Afghanistan.
On its side of the border, the Pakistani military has been involved in a multi-year campaign against domestic Taliban elements located mostly in the mountainous northwest. Also according to Islamabad, its citizens have borne the brunt of the war on terror with thousands killed over the years in militant violence.
In the latest incident, police said a suspected bomb blast at a funeral for a tribal elder in the Lower Dir region killed at least two people Thursday.
While no one immediately claimed responsibility, the area is close to the Afghan border and has seen violence between Islamist militants and Pakistani security forces.
U.S. officials have long urged Islamabad to expand its operation against other groups, such as the Haqqani network which has ties to both the Taliban and al-Qaida.
Pakistani officials insist that they want to solidify their gains before tackling other regions of the remote area of the country.
Analysts also say this back-and-forth in relations between the two countries has been further complicated since the covert U.S. raid deep into Pakistan killed al-Qaida leader Osama bin Laden in May. Washington had not shared any prior knowledge of the raid with its much touted ally in the war on terror in part due to fears someone might have warned bin Laden.
Some information for this report was provided by AFP and Reuters.