KABUL, Afghanistan – The United States stepped up pressure on Pakistan Thursday as Defense Secretary Leon Panetta said “we are reaching the limits of our patience” with a nominal ally that continues to provide a safe haven to al-Qaida-linked militants.

It was the latest sign that the U.S. 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 before to squeeze insurgents who find sanctuary within its borders.

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-Qaida-linked Haqqani terrorist network.

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,” Panetta said.

The U.S. 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.

The U.S. has given Pakistan billions of dollars in aid to support both its government and the fight against Islamist militants..