"When it comes to our military assistance, we're not prepared to continue providing that at the pace that we were providing it unless and until we see certain steps taken," State Department spokeswoman Victoria Nuland said.
The United States was particularly "looking to improve our cooperation in counterterrorism, in counterinsurgency," she told journalists.
Nuland recalled that on May 25 Islamabad demanded that about 100 US advisers leave Pakistani soil, effectively halting military training, adding "we obviously can't do that in an environment where Pakistan has asked our trainers to go."
US President Barack Obama's chief of staff, William Daley, confirmed in a television interview on Sunday that the United States has decided to withhold almost a third of its annual $2.7 billion security assistance to Islamabad.
US Secretary of State Hillary Clinton said Monday the decision to suspend part of the security aid to Pakistan "does not signify a shift in policy."
"Our relationship with Pakistan is not always easy, but it's one that we consider vital to our national security and to our regional interest," she told reporters.
"That said the government of Pakistan must take certain steps and we have outlined those steps in more than one occasion to make sure that we can deliver all the military assistance."
Clinton insisted: "Our decision to pause delivery on this portion of security assistance does not signify a shift in policy, but underscores the fact that our partnership depends on cooperation that's always been the case and it must continue to do so."
Her spokeswoman, Nuland, added: "We are working together on how we can improve our relationship particularly in the categories of counterterrorism and counterintelligence."
