The U.S. is declaring the Pakistan-based Haqqani network a terrorist organization, a move that paves the way for tough financial sanctions against the militant group.

Secretary of State Hillary Clinton announced Friday that she had signed a report to Congress that says the network meets the criteria for a terrorist designation. The U.S. says it will also urge other countries to freeze any assets linked to the militant group.

The Haqqani network has been blamed for a series of high-profile attacks on U.S. and NATO forces in Afghanistan, including an attack at the U.S. Embassy in Kabul last year.

The group, which has ties to the Taliban and al-Qaida, is reportedly based in Pakistan's North Waziristan tribal area. It is also believed to have close ties with elements of Pakistani intelligence — a charge Pakistani officials have rejected.

Senior Haqqani commanders said the terror designation shows the U.S. is not sincere about peace efforts in Afghanistan. They told Reuters news agency the move would result in “hardship” for a U.S. soldier held by militants in Afghanistan, Bowe Bergdahl.

The Pakistani embassy in Washington called the U.S. move to blacklist the Haqqani network an “internal matter” for the U.S. It said Pakistan would continue to work with all international partners, including the U.S., in combating terrorism. Earlier , Pakistani officials said the U.S. decision could negatively impact relations between the two countries.

Several Haqqani network leaders are already subject to U.S. sanctions. Clinton faced a September 9 U.S. Congressional deadline for making a decision concerning the entire group.

Congress has been pressing to have the entire network branded a terrorist organization because it is now widely seen as the biggest threat to U.S. and allied forces in Afghanistan.

However, some U.S. officials have expressed concern that placing the network on a blacklist could further damage already fragile relations with Pakistan and slow efforts to negotiate a political settlement to the Afghan war by undercutting talks with the Taliban.

Months of sour relations between the U.S. and Pakistan are only just now easing with July's reopening of crucial military supply lines across the Afghan border. Pakistan had closed the routes after 24 Pakistani troops were killed in a U.S. air strike last year.

The U.S. has been pressing Pakistan to launch a military offensive in North Waziristan, but the Pakistani army has said its forces are stretched too thin to target militants in the tribal agency.

Afghan Interior Ministry spokesman Sediq Sediqqi on Friday welcomed any move by the United States to target the Haqqani network.