"There are clear reasons for this. Pakistan has played a double game for years," she told reporters at the United Nations on Tuesday. "They work with us at times, and they also harbour the terrorists that attack our troops in Afghanistan.
"That game is not acceptable to this administration. We expect far more cooperation from Pakistan in the fight against terrorism."
The White House on Tuesday said it wanted to see Pakistan do more to fight terrorism and that it would likely announce actions to pressure Islamabad within days.
"Our goal is that we know that they can do more to stop terrorism and we want them to do that," White House spokeswoman Sarah Sanders told reporters.
"In terms of specific actions, I think you'll see some more details come out on that in the next 24 to 48 hours."
It comes as Islamabad summons the US ambassador after President Donald Trump tweeted angrily about Pakistani "lies and deceit", with Islamabad summoning the US ambassador.
David Hale was summoned by the Pakistani foreign office late on Monday to explain Trump's tweet, media said. The ministry could not be reached for comment but the US Embassy in Islamabad confirmed on Tuesday that a meeting had taken place.
Trump said the United States had been rewarded with "nothing but lies and deceit" for "foolishly" giving Pakistan more than $US33 billion in aid in the last 15 years.
"They give safe haven to the terrorists we hunt in Afghanistan, with little help. No more!" he tweeted on Monday.
Pakistani Prime Minister Shahid Khaqan Abbasi on Tuesday chaired a National Security Committee meeting of civilian and military chiefs, focusing on Trump's tweet.
The NSC, in a statement issued by the prime minister's office, did not name Trump but spoke of "deep disappointment" at a slew of critical comments coming from US officials over the past few months.
Islamabad bristles at the suggestion that it is not doing enough to fight militants, noting that its casualties at the hands of Islamists since 2001 number in the tens of thousands.
Foreign Minister Khawaja Asif dismissed Trump's comments as a political stunt born out of frustration over US failures in Afghanistan, where Afghan Taliban militants have been gaining territory and carrying out major attacks.
Afghan defence spokesman General Dawlat Waziri said Trump had "declared the reality", adding that "Pakistan has never helped or participated in tackling terrorism".
Jitendra Singh, a junior minister at the Indian prime minister's office, said Trump's comment had "vindicated India's stand as far as terror is concerned and as far as Pakistan's role in perpetrating terrorism is concerned".
Chinese Foreign Ministry spokesman Geng Shuang, asked during a briefing about Trump's tweet, did not mention the United States.
