The first Marines to be deployed to Australia under a deal that will boost the American militaryâ€™s presence in Chinaâ€™s strategic backyard arrived in the northern city of Darwin late Tuesday night, a sign of the growing importance Washington is placing on the Pacific region. The group of about 180 Marines, which will engage in training exercises with the Australian Defense Force during their six-month rotation, is the first contingent of 2,500 American troops to be deployed here by 2017 under an agreement signed in November by President Obama and Australian Prime Minister Julia Gillard. The decision to deploy the Marines to Australia, which had prompted Beijing to accuse Mr. Obama of escalating military tensions in the region, is part of the presidentâ€™s publicly stated strategy of shifting the American militaryâ€™s long-term focus toward the Pacific and an increasingly assertive China. Australian Defense Minister Stephen Smith, who greeted the Hawaii-based Marines during a ceremony on Wednesday morning in Darwin, touched on the changing regional dynamics during an interview with the Australian Broadcasting Corporation â€œThe world needs to essentially come to grips with the rise of China, the rise of India, the move of strategic and political and economic influence to our part of the world.â€ The United States has had military bases in the North Pacific since the end of World War II, but its presence in Southeast Asia was greatly diminished in the early 1990s. Strengthened ties with Australia, one of Washingtonâ€™s foremost allies, will restore a substantial American footprint near the South China Sea, a major commercial shipping route that has been increasingly the focus of Chinese territorial disputes. There has been speculation here in recent weeks about what form any further regional military cooperation between the two long-time allies would take. Ms. Gillard last week confirmed that discussions with Washington were under way about the possibility of flying long-range American surveillance drones from the remote Cocos Islands â€” an Australian territory in the Indian Ocean â€” but said no substantial progress had been made on the issue.