"Pakistan is in a moment of peril," Kerry, chairman of the Senate Foreign Relations Committee, said during a USA Today interview. "And I believe there is not in place yet an adequate policy or plan to deal with it."
Kerry said he also advised administration aides to stop using "Af-Pak" to describe the unified strategy for Afghanistan and Pakistan, because "I think it does a disservice" to both countries.
The Massachusetts senator's comments signal a change from his original reaction when Obama announced the strategy in March, when Kerry said it was a "realistic and bold" plan.
"Obviously the president disagrees with the chairman on this, and the issues he raised are being aggressively worked in the president's new strategy," White House spokesman Tommy Vietor said in an e-mail to USA Today.
Kerry said he wasn't "blasting the president. What I'm saying is that the details have not been fleshed out. We're working hand in hand on it."
Kerry praised Obama's stepped-up attacks against insurgents in Pakistan by unmanned U.S. aircraft, saying they've had "a dramatic impact, and I think that is one of the reasons why people are screaming about it."
Kerry spokesman Frederick Jones said the presidents of Pakistan and Afghanistan plan a joint visit to the United States for meetings in May.