TOKYO (Agencies) - Expressing grave concern over the activities of extremists in Pakistan, US Secretary of State Hillary Clinton has said extremists pose a direct threat to the government of Pakistan as well as to the security of the United States, Afghanistan and a number of other nations in the region. "Pakistan is striving to curb terrorism and playing key role in the war against terrorism," the US Secretary of State said while addressing a joint press conference with her Japanese counterpart Hirofumi Nakasone on Tuesday. When asked about agreement between Taliban and government in Swat, she said the US is studying the agreement and trying to understand the Pakistani government's intention and the actual agreed-upon language. She also hailed Pakistan's role in war against terrorism, saying the operation of security forces at Pak-Afghan border is laudable. Ms Clinton also welcomed Japanese initiatives to convene donor conference to steer Pakistan's out of economic crisis. She said the United States will attend the donors' conference for assistance to Islamabad. Earlier, Japan and United States signed a bilateral military deal to relocate 8,000 US marines from the southern Japanese base of Okinawa to the Pacific island of Guam. Upon arrival here, Clinton said she chose Asia for her first trip "to convey that America's relationships across the Pacific are indispensable to addressing the challenges and seizing the opportunities of the 21st century." In her talks with Japan's leaders and citizens later Tuesday, she said, "We will be looking for ways to collaborate on issues that go beyond just our mutual concerns to really addressing the global concerns." She said these would include "climate change and clean energy, Afghanistan, Pakistan, nuclear proliferation and other common concerns. Meanwhile in Brussels, NATO expressed concern on Tuesday after Pakistan signed a pact with extremists to introduce Sharia law in the Swat valley to try to take the steam out of a Taliban uprising there. "We would all be concerned by a situation in which extremists would have safe haven," NATO spokesman James Appathurai told a news briefing. NATO heads an international force battling Taliban militants in Pakistan's neighbour Afghanistan and Appathurai said he did not know if the pact would make its task more difficult. However, he added: "It is certainly reason for concern." Appathurai said NATO did not doubt the commitment of the Pakistani government and its President Asif Ali Zardari to fighting extremism. Zardari's wife, Benazir Bhutto, was killed by militants. He said NATO and Pakistan wanted to deepen their cooperation in the fight against militants. "But it remains the case, without doubting the good faith of the Pakistani government, that this region is suffering very badly from extremism and we would not want to see that get worse." An uprising erupted in Swat in 2007, and militants now control the alpine valley just 130 km northwest of Islamabad. The agreement to introduce Islamic law was reached at talks between Islamists and officials of NWFP government in Peshawar on Monday. The US envoy for Pakistan and Afghanistan, Richard Holbrooke, said on a trip to India on Monday the situation in Swat showed the United States, Pakistan and India faced a common enemy. Meanwhile, UK said on Tuesday that it is concerned over an agreement for the introduction of Islamic courts in parts of NWFP as 'previous peace deals have not provided a comprehensive and long-term solution' to problems in the insurgency-hit Swat valley. NWFP govt and leader of a pro-Taliban banned Islamic group signed a deal on Monday, abolishing unIslamic laws and setting Islamic courts in Malakand Division. The courts will also be set up in Swat valley where Pakistani Taliban have been fighting against the security forces over the past two years. 'We need to be confident that they will end violence - not create space for further violence', UK High Commission spokesperson Jennifer Wilkes said in a statement. Meanwhile Sufi Muhammad, chief of banned Tehrik Shariat-e-Nifaza Muhammadi (TSNM), on Tuesday led thousands of his followers to arrive in Swat to convince the local Taliban to lay down arms and accept the agreement on Islamic laws. Sufi Muhammad, father-in-law of Maulana Fazalullah, the chief of Swat Taliban, will meet Fazaullah on Wednesday, sources said. Sufi Muhammad, who was released last year after seven years in a prison for illegally crossing into Afghanistan in 2001 to support Taliban, set up camps in Mingora, the main city in Swat and will stay there unless peace is restored.