His comments came days after US President Donald Trump hit out at Pakistan for providing safe haven to "agents of chaos" that kill Americans in Afghanistan and warned Islamabad that it has "much to lose" by harbouring terrorists.
"We will be able to see when these changes start to happen. They might not become immediately apparent to the public, but we're confident that when Pakistan takes the steps we're asking it to do, we'll know it and we'll be able to assess," the official said.
"And so, our security aid will be conditioned on the steps that we expect them to take against, in particular, the Taliban-Haqqani Network," the official said, adding the US is monitoring the situation carefully in Pakistan and expects some progress.
The official was responding to a series of question on the statements coming out of Pakistan, which are generally in strong opposition to Mr Trump's South Asia strategy. On whether Pakistan will cooperate with the US this time after the war of words, the official said, "I think the President was very clear that we are going to take a different approach to that stand. There's a lot of frustration with the continued safe havens in Pakistan," the official said.
"But we believe there is hope for greater cooperation from Pakistan on these issues. It's Pakistan's choice. Pakistan has much to benefit from by cooperating with the US and cracking down on some of these groups," the official said.
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