NATO warned Tuesday that Pakistan risked creating a safe haven for Islamist extremists after it struck a deal to impose Islamic law and suspend a military offensive in the former tourist haven of Swat. Criticism of the truce mounted as a hardline cleric dispatched by the government to convince the Taliban to stop fighting as part of the deal arrived in the Swat Valley's main city of Mingora to a hero's welcome. NATO says it has 55,000 troops across the border in Afghanistan, and many of them have come under attack by Taliban and al-Qaida fighters believed to have sought refuge in pockets of Pakistan's northwest. “It is certainly reason for concern,” NATO spokesman James Appathurai said in Brussels about the latest deal. “We should all be concerned by a situation in which extremists would have a safe haven. Without doubting the good faith of the Pakistani government, it is clear that the region is suffering very badly from extremists and we would not want it to get worse.” Britain also weighed in with reservations. “Previous peace deals have not provided a comprehensive and long-term solution to Swat's problems,” said a statement from the British High Commission in Islamabad. “We need to be confident that they will end violence _ not create space for further violence.” In Japan, Secretary of State Hillary Clinton said the Pakistani move still needed to be “thoroughly understood.” She was on her first visit to Asia since taking up the post. A senior US defense department official described the deal as a “negative development.” In Swat, the dispatched cleric, Sufi Muhammad, said he was hopeful the Taliban would cooperate with the agreement. “We will soon open dialogue with the Taliban. We will ask them to lay down their weapons. We are hopeful that they will not let us down,” Muhammad told reporters. “We will stay here in the valley until peace is restored.” Residents lined the route as his caravan of 300 people drove through, waving and shouting “Long live peace! Long live Islam!” Extremists in Swat have beheaded opponents and torched scores of girls schools in recent months, while gunbattles between security forces and militants have killed hundreds. Up to a third of the valley's 1.5 million people have fled and the scenic area is now believed to be mostly under militant control.