Washington: The United States has asked Pakistan to expel terrorists, especially the Taliban leaders, operating from terror safe havens within its soil, a top Trump administration official today said.

"We've had a number of discussions with our Pakistani partners on expectations for change and expelling terrorists from areas in which they've been allowed to operate," Deputy Secretary of State John Sullivan told members of the Senate Foreign Relations Committee during a Congressional hearing on Afghanistan.

He was responding to questions from lawmakers expressing concerns over Pakistan's approach fighting terrorism.

"They (Pakistan) understand what we expect...Our suspension of security assistance continues until we see more evidence that they are in fact taking action," Sullivan said.

He said the US has been in discussions with Pakistan but there has been not a "sufficient amount of action" from it against terrorists.

Senator Bob Corker, Chairman of the Senate Foreign Relations Committee, supported the South Asia Policy of the Trump administration.

"This administration has rightly drawn a clear line with Pakistan, suspending security assistance of over a USD billion as long as Islamabad continues to shelter Haqqani, and other terror groups that target innocent civilians, as well as the US and allied forces," he said.

Corker had blocked the sale of F-16 fighter jets to Pakistan during the previous Obama administration.

He said this "pointed approach" is designed to confront Pakistan's "duplicity" and its actions to provide safe harbor to the "greatest threat to our efforts in Afghanistan".

Last month, the Trump administration had suspended nearly USD 2 billion in security assistance to Pakistan because of its inability to take actions against terror groups.

Senator Ben Cardin, Ranking Member of the Senate Foreign Relations Committee, said such a policy might not work.

"Does the administration really believe that a simple suspension of security assistance is going to bring about a lasting commitment by Pakistan to drop support for the Afghan Taliban or the Haqqani Network. It hasn't before," he said.

"We've tried it several times over the past 16 years. I have little confidence that such behavioural change is coming. So are we prepared to do more to elicit the behavioural change we want or is this just more about the same?" Cardin asked.

Sullivan said the Trump administration may consider lifting the suspension, when it sees decisive and sustained actions from Pakistan to address the US concerns, including targeting all terrorist groups operating within its territory, without distinction.

"The US is committed to doing our part to reduce tensions in the region in ways that address Pakistan's legitimate concerns," he said.

Sullivan said the US opposes the use of terrorist proxies by any country against another country anywhere in the world.

"The use of terrorism has no place in a rules-based international system. We hope the Pakistanis will also help to convince the Taliban to enter into a peace process," he said.

Sullivan told lawmakers that it was the assessment of the US that Pakistan has not done enough to expel elements of the Taliban that have been operating in sanctuaries in Pakistan and easily able to cross the border into Afghanistan.

Pakistan, he said, certainly have the ability to urge the Taliban to do come to the peace talks.

"What we believe they do have the ability to do also is to expel them from sanctuaries in their country. They may not be able to actually drive them to the negotiating table, but they can help and they can eliminate sanctuaries in their country where they currently operate," he said.

Noting that Pakistan has suffered grievously from terrorist attacks, Sullivan said what the US is looking for from Pakistan is more support against terrorist organisations.

"I understand it's a delicate balance for Pakistan. We want to do all we can to support them in that effort, and we have provided an enormous amount of assistance, monetary and otherwise, to the Pakistani government.

"What we're looking for is an indication from them, more support directed at those outward-focused terrorist organisations," he said.