Clinton told a House appropriations subcommittee that the Obama administration is working to persuade the Pakistani government that its traditional focus on India as a threat has to shift to Islamic extremists.
"Changing paradigms and mind-sets is not easy, but I do believe there is an increasing awareness of not just the Pakistani government but the Pakistani people that this insurgency coming closer and closer to major cities does pose such a threat," she said.
On Wednesday, Clinton told another House committee that in her view the Pakistani government is "basically abdicating to the Taliban and the extremists."
She said Thursday that the administration's special envoy for Pakistan and, Richard Holbrooke, has had "painful, specific" conversations with a wide range of Pakistanis about the need to act more effectively against the insurgents.
"There is a significant opportunity here for us working in collaboration with the Pakistani government to help them get the support they need to make that mind-set change and act more vigorously against this threat," she said, adding, "There are no promises. They have to do it."
Clinton encountered skepticism from some committee members who expressed doubt about succeeding in Pakistan. Rep. David Obey, D-Wis., told her he worries that the administration's policy agenda - domestic and foreign - could be "devoured" by the Pakistan-Afghanistan problem.
"I have absolutely no confidence in the ability of the existing Pakistan government to do one blessed thing," Obey said.
Rep. Nita Lowey, D-N.Y., the committee chairwoman, expressed similar concerns.
"The escalating terrorist violence in Pakistan and that government's inability and unwillingness to confront the extremist threat undermine any progress we have made in Afghanistan and complicates future efforts there," Lowey said. "I fear that we are losing the window of international consensus and commitment to help the region gain a strong foothold on its long climb out of conflict."
One measure of progress in Pakistan, Clinton said, is the extent to which the Pakistani military is shifting its troops from the Indian border to the Afghan border, where the Taliban threat has been expanding.
Clinton was appearing before the appropriations panel that is reviewing the administration's request for $7.1 billion in additional funds for the State Department this budget year. Of that total, $497 million would be for State Department support of Pakistan and $980 million would be for Afghanistan. About $482 million would be for Iraq.
Clinton said that local job creation is a key purpose of the extra funds requested for State Department work in Afghanistan.
She told the panel that a main goal is to improve security at the local level in Afghanistan by putting more people to work. And she said the administration believes that many in the Taliban insurgency who are fighting against U.S. and Afghan forces are motivated more by money than ideology.
"The U.S. is having a very hard time understanding exactly why it is that one of the world's larger armies, armed with nuclear weapons, cannot fight and win a war against these rag-tag militants," said one Western military official, who spoke to CBS News on condition of anonymity.
Clinton defended President Barack Obama's effort to engage diplomatically with Iran, calling it a reasonable alternative to what she called a failed Bush administration policy.
"We tried the policy of total isolation for eight years," she said in a rising voice, "and it did not deter Iran one bit. The nuclear program has continued unabated. They weren't supporting Hamas before. They are supporting Hamas now."
Clinton said it remains unclear whether international pressure on Iran will compel it to change course.
"Sanctions are a tool for us to leverage pressure on the Iranian regime to change behavior that we obviously consider serious threats," she said. "And so we are talking with our partners about additional sanctions as part of an incentives-disincentives approach to Iran. It's a difficult balancing act."