KABUL (Reuters) - Secretary of State Hillary Clinton said Thursday she was looking for a "reality check" on a visit to Afghanistan, where she also pushed for closer cooperation with neighboring Pakistan on both the war and economic development.

Clinton will fly on to Islamabad, a U.S. official said, where she will also urge officials to work more closely with counterparts across the border. She presented a new summary of the mission in both countries: "fight, talk, build."

The message is that all three countries should aim to fight against irreconcilable militants, talk with those willing to negotiate, and meanwhile keep building on the economic side.

"We're going to be fighting, we're going to be talking and we're going to be building. And they can either be helping or hindering, but we are not going to stop our efforts," Clinton said at a news conference with Afghan President Hamid Karzai.

"It is a time for clarity. It is a time for people to declare themselves as to how we are going to work together."

Clinton also said the door was still open to the Taliban to negotiate an end to the war in Afghanistan, but they would face "unrelenting" attacks if they did not.

Pakistan's cooperation was critical to any peace process, particularly ensuring that insurgents could not find shelter in the country, she said.

"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 cross the border to kill in Afghanistan," Clinton said.

Earlier in the day she told Afghan civil society leaders that she had seen progress in their country, and remained hopeful about the prospects for a peaceful and stable future.

"I'm here to have a reality check," Clinton said at a meeting at the U.S. embassy in Kabul.

Clinton's arrival Wednesday on an unannounced visit to Kabul followed several high-profile attacks in the Afghan capital, including an assault on the U.S. embassy in September and days later the assassination of President Hamid Karzai's top peace envoy, former president Burhanuddin Rabbani. Ties between Kabul and Islamabad have been particularly strained since the assassination of Rabbani, who was killed by a suicide bomber posing as a Taliban reconciliation envoy.

Many Afghans, including senior officials, have accused the Pakistan government of having links to the killing, and say their neighbor is fomenting instability to further its own political interests. Pakistan denies this. Karzai has been more circumspect, but hinted after the killing that he had lost hope in pursuing peace talks with the Taliban and suggested negotiations with Pakistan instead. Top U.S. officials have also accused Pakistan of supporting insurgent groups in Afghanistan after September's 20-hour attack on targets in Kabul, including the U.S. embassy.

(Editing by Paul Tait)

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