Australia,a key US ally,today welcomed the enhanced American presence in the Asia-Pacific,a day after the Pentagon announced it is shifting a bulk of its naval fleet to the region by 2020 under a new strategic focus on Asia. Defence Minister Stephen Smith said the US move would have "the positive impact" in the region. At the annual Shangri-La Dialogue conference in Singapore on Saturday,US Defence Secretary Leon Panetta detailed a five-year plan for 60 per cent of the fleet to be assigned to the Pacific by 2020,as part of a new strategy to increase the US presence in Asia. Smith,speaking shortly after his return from Singapore,said the United States' presence in the Asia Pacific had been "a force for peace and stability and prosperity since the end of World War II." "We welcome very much the fact that not only will the United States continue that engagement,it will enhance it," he told the Australian Broadcasting Corporation. "The essential point is that none of this is done for reasons of trying to maximise or influence concern or threat; it's all done for purposes of stability to continue peace,to continue prosperity." "Some seem to assume that the economic and strategic influence of the United States,the world's largest economy and superpower,will somehow be rapidly eclipsed overnight as a result of the new distribution of power to Asia," he said. The boost in naval presence could increase tensions with China,whose leaders have expressed unhappiness at any larger US presence in the Asia-Pacific region. America and Australia have already announced that around 2,500 US Marines will be deployed in the Northern Territory as part of enhanced defence cooperation,as outlined by President Barack Obama during a visit to the country in November.