WASHINGTON — The Obama administration is considering placing the Haqqani network on its list of terror groups after blaming the militants for deadly attacks in Afghanistan, a US official said Monday.

Seven leaders of the Haqqani network, which operates from safe havens in Pakistan and was founded by former CIA asset Jalaluddin Haqqani and is run by his son Sirajuddin, have been placed under US sanctions since 2008.

The top US military officer, Chairman of the Joint Chiefs of Staff Admiral Mike Mullen, directly accused Pakistan's intelligence service on Thursday of supporting the Haqqani network's attack on the US embassy in Kabul, a truck bombing on a NATO outpost and a June attack on Kabul's InterContinental hotel.

Sangeen Zadran, Sirajuddin and Badruddin Haqqani have been designated by the State Department, while the Treasury has targeted four other Haqqani leaders: Nasiruddin Haqqani, Khalil Haqqani, Ahmed Jan Wazir and Fazl Rabi.

"Certainly FTO (foreign terrorist organization) designation is something under review," State Department spokesman Mark Toner told reporters.

"But the idea that we haven't gone after the Haqqani Network at all I think is a mischaracterization."

Washington has asked Islamabad in vain to launch on offensive in the restive tribal region of North Waziristan, a Haqqani bastion bordering Afghanistan.

"We believe that these kind of safe havens are extremely troubling and indeed a matter of great concern and dangerous development for both the United States and for Pakistan. So we want to see action taken against them," Toner said.

The spokesman acknowledged "very clear challenges" in the US relationship with Pakistan, but insisted that President Barack Obama's administration was committed to "working constructively" with Islamabad.

Pakistani Prime Minister Yousuf Raza Gilani has called a rare cross-party conference for Thursday, although he dismissed the American allegations as little more than finding a scapegoat for US "disarray" in Afghanistan.

And his army chief scrapped a visit to London on Monday as Islamabad refused to bow to mounting US demands for action against the Al-Qaeda-linked Haqqani extremists.

The alliance between Pakistan and the United States in the 10-year war in Afghanistan and against Al-Qaeda hit rock bottom this year in the wake of the unilateral American raid that killed Osama bin Laden near Islamabad on May 2.