KABUL, Afghanistan (AP) — U.S. Secretary of State Hillary Rodham Clinton on Thursday demanded that Pakistan step up the fight against terrorists within its borders, delivering a blunt message that Pakistanis "must be part of the solution" to the ongoing conflict in neighboring Afghanistan.

Using unusually stern language, Clinton said while visiting the Afghan capital of Kabul that the Obama administration expects the Pakistani government, military and intelligence services to "take the lead" in not only fighting insurgents based in Pakistan but also in encouraging Afghan militants to reconcile with Afghan society.

"We intend to push Pakistan very hard," Clinton told a joint news conference with Afghan President Hamid Karzai. Clinton will travel to Pakistan later Thursday to deliver the message wrapped in a new formula called "fight, talk, build" that aims to kill unrepentant insurgents, convince those willing to accept certain principles to make peace, and rehabilitate Afghanistan and integrate it back into the region.

"Our message (to Pakistan) is very clear," she said. "We’re going to be fighting, we are going to be talking and we are going to be building … and they can either be helping or hindering, but we are not going to stop."

Clinton, who will be leading an extraordinarily high-level U.S. delegation to Islamabad to make that case, said it was imperative for the U.S., Afghanistan and Pakistan to cooperate. But she said Pakistan bears much of the responsibility.

"We must send a clear, unequivocal message to the government and people of Pakistan that they must be part of the solution, and that means ridding their own country of terrorists who kill their own people and who cross the border to kill people in Afghanistan," she said.

The U.S. sees a political settlement with the Taliban as key to ending the war and is pushing Karzai to lead and expand a reconciliation drive, although the Taliban has indicated no public interest in such a deal. A secret U.S. effort to spark negotiations earlier this year angered Karzai, although he had nothing but kind words of welcome for Clinton.

"Reconciliation is possible," she said. "Indeed, it represents the best hope for Afghanistan and the region."

Clinton’s tough comments come as Karzai has expressed frustration with his attempts to woo Taliban fighters away from the insurgency amid increasing attacks by the Taliban-allied, Pakistan-based Haqqani network and the murder last month of elder statesman Burhanuddin Rabbani, who was leading the outreach. Rabbani was killed when he greeted a suicide bomber posing as a Taliban emissary bearing a reconciliation message.

Karzai said Rabbani’s assassination made it clear that Pakistan must be on board and involved in reconciliation efforts.

"It brought us to the point where we felt that those who come to talk to us on behalf of the Taliban actually represent assassinations and killings and not a peace process, and therefore the focus of the peace process, we felt, would serve a better purpose taken to Pakistan," Karzai said as Clinton stood beside im in the garden of the presidential palace.

"We believe that the Taliban, to a very, very great extent — a very, very great extent — are controlled by establishments in Pakistan, stay in Pakistan, have their headquarters in Pakistan and launch operations from Pakistan," he said. Therefore, he said, the proper "authority" and "venue" for any peace talks is Pakistan.

Clinton was clearly sympathetic to his argument.

"This is a time for clarity, it is a time for people to declare themselves as to how we are going to work together," she said, referring to Pakistan.

In Islamabad later Thursday, Clinton will be meeting up with CIA chief David Petraeus and the nation’s top military official, Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey, for talks with senior Pakistani officials.

Their presence will be a muscular show of diplomatic force that several officials described as a combined message of support and pressure.