Islamabad, Pakisan ? Vice President Dick Cheney made a surprise visit Monday to Pakistan to bluntly tell President Pervez Musharraf that his forces must markedly heighten their efforts to track down al-Qaida militants crossing the border into Afghanistan.

But Pakistan was defiant in its response to Cheney’s message, blaming the increased violence in the region on lapses in security on the Afghan side of the border.

“Our reading is that there are security failures inside Afghanistan,” said Nadeem Kiani, a spokesman for the Pakistan Embassy in Washington. “It doesn’t have much to do with Pakistan.”

Kiani also suggested that the Afghan-Pakistani border is not as porous as the one between the U.S. and Mexico.

The Bush administration has said it expects al-Qaida and the Taliban to launch a spring offensive against U.S. and Afghan troops from its staging areas in the tribal areas that straddle the Afghan-Pakistani border.

To prepare for new attacks, the U.S. is increasing its forces to 27,000, the highest level since a U.S.-led invasion drove out the Taliban government in 2001.

While Cheney made no comment to journalists about his meeting with the Pakistani president, the public nature of the American message was a departure from the past, in which the U.S. would praise Musharraf’s regime publicly and make its criticisms in private.

Musharraf’s office released a statement saying, “Cheney expressed U.S. apprehensions of regrouping of al-Qaida in the tribal areas and called for concerted efforts in countering the threat.”

Cheney also “expressed serious U.S. concerns on the intelligence being picked up of an impending Taliban and al-Qaida ‘spring offensive’ against allied forces in Afghanistan.”

Pakistan says it has more than 1,000 border posts on its side of the 1,400-mile-long border of Pakistan and Afghanistan, while there are only 100 posts on the Afghan side.

While U.S. and British officials have publicly praised Pakistan’s anti-terrorist operations in the past five years, there has been a growing sense of unease about militants operating freely in tribal areas and infiltrating into Afghanistan. The militants are operating in the same region where some believe Osama bin Laden, the mastermind of the Sept. 11, 2001, attacks against the U.S., is still hiding out.

“The administration is beginning to recognize that it has to combine some public pressure with the private remonstrations in dealing with Musharraf,” said Husein Haqqani, director of the Center for International Relations at Boston University. “In the last five years, the U.S. policy has been that any criticism of the Musharraf government be made in private, while all the praise has been public. It has made Musharraf think he’s the only chef in town – he can serve any dish he wants.”

Cheney’s message may spell the beginning of a changed relationship between the U.S. and Pakistan. “The administration is going to stop giving Musharraf a totally free hand,” said Haqqani, who was an adviser to three previous Pakistani prime ministers. “Instead, Cheney might put forward a laundry list of things that need to be done, and there will be a lot more active monitoring of compliance.”

After stopping in Islamabad, Cheney made a second secrecy-shrouded visit, going to Afghanistan for meetings with Afghan President Hamid Karzai. In the vast, largely lawless border region, the Bush administration is also trying to bolster U.S. and NATO efforts to help the Afghan government withstand any resistance by the Taliban and other armed groups.