ZAGREB (AFP) - World leaders Tuesday mourned the death of veteran US diplomat Richard Holbrooke, lauding the dogged negotiator as a colossus who against the odds brokered peace in conflict zones such as Bosnia. US President Barack Obama led the tributes to his special envoy to Afghanistan who died on Monday, calling him a true giant of American foreign policy who has made America stronger, safer, and more respected. Balkan leaders praised Holbrooke for bringing stability to their region. But with war still raging in Afghanistan, Afghan President Hamid Karzai, with whom Holbrooke had strained relations, struck a more nuanced note, pointedly terming his death as a loss for the American people. UN chief Ban Ki-moon paid tribute to a man of history, saying Holbrooke was a giant and a legend in his time. The advice on which so many relied reflected the rich breadth and challenge of his extraordinary career, Ban added. He was big-hearted and outsized in every way, not least in his capacity for friendship and uncommon humanity. Former Croatian foreign minister Mate Granic, who was at the Dayton negotiations, said Holbrooke, who died after emergency heart surgery for a torn aorta, was one of the greatest US diplomats of the past 20 years. Holbrooke always set a clear goal. He was a good tactician, a great diplomat who knew how to use the power of the US, said Granic, who was foreign minister from 1993 until 2000. And Hashim Thaci, the former guerrilla leader who is now Kosovos prime minister, said the territory had lost an important friend who had always defended Pristinas interests. US Secretary of State Hillary Clinton spoke of a sad day for her and for the United States. Tonight America has lost one of its fiercest champions and most dedicated public servants, Clinton said. In a twist of fate, Holbrooke died almost 15 years to the day since the signing of the Dayton accords on December 14, 1995. European Union foreign policy chief Catherine Ashton praised Holbrooke as a remarkable man, a true diplomat and a champion of peace and reconciliation, not just in Pakistan and Afghanistan, but throughout the world. Canadian Foreign Minister Lawrence Cannon said Canada had lost a friend and an inspiration to us all. British Prime Minister David Cameron said Holbrooke was an indefatigable champion in the cause of peace, who worked tirelessly for a better world. Swedish Foreign Minister Carl Bildt, who worked closely with him and others to broker the Dayton accords, said the US diplomat played an absolutely decisive role in forging the pact. Soldiers die in battle, but diplomats seldom do. Richard Holbrooke was I think an exception in this respect. He died in the middle of one of modern diplomacys most difficult and most important battles, Bildt wrote. Holbrooke faced perhaps his toughest challenge pushing Kabul and Islamabad to work together against resurgent Al-Qaeda and Taliban militants as Obamas special US envoy in the Afghan conflict. In Kabul, General David Petraeus hailed Holbrooke as a true titan in the diplomatic arena and a central figure in the effort in Afghanistan and Pakistan. His death is a tragic loss for the two countries and our world, Petraeus said.