KABUL, Afghanistan — The United States stepped up pressure on Pakistan Thursday, as Defense Secretary Leon E. Panetta said "we are reaching the limits of our patience" with a nominal ally that continues to provide a safe haven to al Qaeda-linked terrorists.
It was the latest sign that the United States is now getting tougher with Pakistan after years of muting criticism and looking the other way on the premise that an uneasy friendship was better than making the nuclear-armed country an outright enemy.
As U.S. forces draw down in neighboring Afghanistan, the Americans appear to be pushing Pakistan harder than ever to squeeze Islamist insurgents who find sanctuary within its borders.
Mr. Panetta, in the Afghan capital, told reporters he was visiting Kabul to take stock of progress in the war and discuss plans for the troop drawdown.
But he used a press conference to strike across the border instead, saying the Pakistani government needs to do more - and soon - to root out the al Qaeda-linked Haqqani terrorist network.
Mr. Panetta repeatedly emphasized U.S. frustration with attackers crossing the border from Pakistan. It is essential that Pakistan stop "allowing terrorists to use their country as a safety net in order to conduct their attacks on our forces," he said alongside Afghan Defense Minister Abdul Rahim Wardak.
"We have made that very clear time and time again, and we will continue to do that; but as I said, we are reaching the limits of our patience," Mr. Panetta said.
The Obama administration clearly wants Pakistan to take on the Haqqanis before the bulk of U.S. troops have left the region by the end of 2014. After that, the Afghans would have more trouble contending with the militants, who carry out large-scale attacks in Kabul and elsewhere.
"There may be an increasing realization within the U.S. government that we have a few more years to really go after this problem and time is running out," said Jeffrey Dressler, an analyst at the Institute for the Study of War in Washington.
Mr. Panetta's remarks capped a week of some of the boldest language and actions by the administration against its stated ally.
Just a day before, he stood in the capital of Pakistan's arch rival, India, and declared that drone strikes against terrorist suspects would continue, dismissing Pakistan's claims of sovereignty by noting that U.S. sovereignty was jeopardized as well.
A senior U.S. official acknowledged Thursday that the recent increase in drone strikes on insurgents in Pakistan, targeting mostly al Qaeda but other militants as well, is partly a result of frustration with Islamabad.
Earlier this week, NATO reached agreements to ship tons of supplies out of Afghanistan through northern and western countries, bypassing Pakistan, which has kept its borders closed to NATO trucks in response to the killing of 24 Pakistani troops by NATO forces.
The United States has given Pakistan billions of dollars in aid to support both its government and the fight against Islamist militants. The Pakistani military has battled insurgents who attack Pakistani targets but has largely avoided taking on terrorists like the Haqqanis whose sights are set across the border.
The Haqqanis, who also have ties to the Taliban, have emerged as perhaps the biggest threat to stability in Afghanistan.