Defending his troop surge strategy, US President Barack Obama said Thursday that things in Afghanistan are getting better not worse and his plans to start withdrawing US forces next year are on track.In an interview with Australian television ahead of an Asian visit, Obama also indicated that Washington will maintain efforts to get China, India and other developing countries to make further commitments to fighting global warming.Obama confirmed he will visit Canberra and Sydney in June — a rescheduled a visit after he deferred plans to visit staunch ally Australia and nearby Indonesia last month to conduct last-minute lobbying on his health care reforms.Afghanistan is likely to be a key topic for discussion when he holds talks with leaders in Australia, which has some 1,500 troops in the country — the largest single contingent outside NATO — and has suffered 11 combat deaths.Obama said the war in Afghanistan remained a difficult task but that there had been positive trends recently.Obama ordered tens of thousands more troops into Afghanistan last year, and operations in recent months have pushed into parts of southern Afghanistan where Taliban rebels are strongest. Coalition forces have taken the insurgent stronghold of Marjah, and are gearing up for an operation in the Taliban movement's birthplace of Kandahar.But US combat deaths have risen this year and the Red Cross says roadside bombings and other violence blamed on the Taliban has also increased."I would dispute the notion that it is not getting better" in Afghanistan, Obama told the Australian Broadcasting Corp. in the interview, conducted in the White House and broadcast in evening prime time in Australia."I do think that what we have seen is a blunting of the momentum of the Taliban, which had been building up in the year prior to me taking office," he said.Obama reiterated his plan to begin drawing down US troops in 2011 and handing responsibility for security to domestic forces in Afghanistan."We can't be there in perpetuity," he said. "Neither the American people nor the Australian people should be asked to carry that burden any longer than it needs to be carried."On China, Obama said the United States was not interested in constraining the Asian giant's booming growth or its emergence as a world power but that the country must take seriously the responsibilities that come with that role.Asked about China's commitment to fighting global warming, Obama said China's leaders understand they need to decide on a new model that allows the country to pursue growth while also protecting the environment."Right now though, their impulse is to say, well, we'll let the developed countries, the Australias and the Americas, deal with this problem first and we'll deal with it when we've caught up a little bit in terms of our standard of living," he said."The point we've tried to make is that we can't allow China to wait."Hesaid the global agreement on climate change struck last year inCopenhagen was a sign of progress, but that the world "has to do more."Chinaand the United States are among the world's largest emitters of thegases that cause global warming, but Obama said "no two countries candictate a solution" to the problem.He said developed andemerging countries must both find ways of reducing their emissions ofthe gases that are causing global warming."If emergingcountries, not just China, but India, Brazil, and others, are pursuinga path in which they replace us as the largest carbon emitters, that isnot a sustainable, practical approach," he said.