Secretary of State Condoleezza Rice has expressed disappointment with a deal between Pakistan and pro-Taliban militants.
In September, Pakistan signed an agreement with tribal leaders in its North Waziristan region, along the border with Afghanistan, meant to stop cross-border attacks. The US military says the area has since become an even stronger haven for Taliban and Al-Qaeda fighters.
Rice told lawmakers on Friday that the United States has tried to support Pakistani President Gen. Pervez Musharraf's plan to empower tribal leaders to deal with crossborder problems.
But, she said, "Frankly, there have been some problems and some disappointments with that plan."
Pakistan insists it is doing all it can to stop crossborder militancy and has deployed about 80,000 troops along its rugged border with Afghanistan.
Rice said the United States has been clear with Musharraf that he must do something about cross-border problems.