Charging that violent extremist groups from their safe havens in Pakistan were posing a "significant threat" to US forces, a top Pentagon official has warned that Washington would "consider a range of options" if Islamabad does not address these concerns.

"It is Pakistan's responsibility to prevent attacks from its territory on others, including Afghanistan and our forces there," Mark Lippert said in his testimony before the Senate Armed Services Committee during his confirmation hearing for the post of the Assistant Secretary of Defence for Asian and Pacific Security Affairs.

"If Pakistan does not address these threats, the United States will have to consider a range of options, but it is best when we have Pakistan's cooperation," he told lawmakers in a written response to the question asked to him.

"The ability of violent extremist groups to find support and safe haven in Pakistan poses a significant threat to US forces, the NATO mission, and the long term stability of Afghanistan," he said, adding that attacks against US and coalition personnel are unacceptable.

Noting that Pakistan has legitimate concerns that should be understood and addressed by the Afghan Government in any process to bring about a stable and durable political solution in Afghanistan, he said at the same time Pakistan also has responsibilities of its own, including taking decisive steps to ensure that the Afghan Taliban and affiliated groups cannot continue to conduct the insurgency from its territory.

"Increased action is particularly critical with groups such as the Haqqani network, who continue to maintain close ties to Al-Qaeda and other violent extremist organizations that pose real threats not only to the United States, but also to the people and Government of Pakistan," he said.

"Pakistani military leaders cannot pick and choose amongmilitant groups," Lippert said.

"However, Pakistan remains a critical country in the fight against terrorists. Therefore, I believe we should continue to work closely with Pakistan to act against the extremists that threaten US and Pakistani security, and pursue a stable, peaceful, and prosperous region," he added.

Lippert said going forward, it is vital that Pakistan live up to its responsibilities, including to cooperate fully in counter-terrorism matters, to expand its counterinsurgency campaign against all extremists and militant groups that have found safe haven inside Pakistan.

"I understand that in the wake of the Osama bin Laden raid, the Administration asked Pakistan to take a number of concrete steps to demonstrate its continued commitment to a cooperative and mutually beneficial relationship. Future provision of security-related assistance will be informed by Pakistan's response to these requests," he said.

Lippert said he believe that America's interests in the region and in Asia more broadly require a stable and constructive relationship
with Pakistan.

"The fact that Pakistan is a nuclear state that faces internal threats from extremist organisations adds to the importance of a continued relationship with Pakistan," he said.

"Preventing, if possible, a potential Pakistan-India conflict is another important strategic interest. It is in the United States' interest for Pakistan to have a strong, civilian-led government and an open society, to live in peace and security with its neighbors,
and to ensure its nuclear assets remain secure, in accordance with international standards," he said.