WASHINGTON -- In a move that risks reopening deep fissures in relations with Pakistan, the Obama administration will designate the deadliest Afghan insurgent group as a foreign terrorist organization, Secretary of State Hillary Clinton told Congress Friday.

The decision to designate the Haqqani network, a Taliban-allied extremist organization based on Pakistan’s side of the mountainous border with Afghanistan, was made under pressure from Congress and avoids Republican election-year criticism that the administration is too accommodating toward Pakistan.

But it also could open the way, some analysts warned, to the U.S. eventually designating Pakistan a state sponsor of terrorism because of the alleged close ties between the Haqqanis and Pakistan’s top intelligence agency, the Inter-Services Intelligence directorate, or ISI. Such a move, which senior State Department officials stressed is not being considered, could jeopardize Pakistan’s cooperation with the Obama administration’s goal of withdrawing all U.S. combat forces from Afghanistan by the end of 2014.

“This is targeted specifically at the Haqqani network. It is not targeted in any way at any organ of the Pakistani government,” said a senior administration official who spoke to reporters on the condition that there be no further identification.

The Haqqani network, based in Miran Shah, the main town in Pakistan’s North Waziristan tribal agency, was an American ally during the 1979-89 Soviet occupation of Afghanistan and was a recipient of U.S. aid funneled to it by the ISI. Its leader, Jallaludin Haqqani, became a minister in the Taliban government that ruled Afghanistan from 1996 until the 2001 U.S. invasion.

In recent years, however, it has been blamed for some of the most spectacular attacks in Afghanistan, including assaults on the U.S. and Indian embassies, and U.S. military officials have tried to persuade Pakistan to take action against it. Testifying before a Senate committee in September 2011, retired Adm. Mike Mullen, then the chairman of the Joint Chiefs of Staff, called the Haqqani network “a veritable arm” of Pakistan’s ISI. The ISI denied the allegations.

The Pentagon on Friday welcomed Clinton’s announcement.

“The Haqqani network represents a significant threat to U.S. national security, and we will continue our aggressive military action against this threat,” Pentagon spokesman George Little said.

The decision follows extensive debate within the administration over whether the designation would be counterproductive, angering Pakistan just as bilateral relations are beginning to recover after U.S-Pakistan ties reached their chilliest point ever, propelled by the May 2011 raid that killed Osama bin Laden and a November 2011 U.S. assault on a border outpost that killed 24 Pakistani soldiers. Some U.S. officials also opposed the decision for fear it would endanger efforts to win the release of Bowe Robert Bergdahl, of Sun Valley, Idaho, a U.S. soldier who has been held by the Haqqanis since June 2009.

Clinton’s hand was forced, however, by legislation that set a deadline for the administration to designate the group as a foreign terrorist organization or explain why it didn’t meet the criteria. President Barack Obama signed the deadline into law last month, giving Clinton until Sunday to respond.