CANBERRA, Australia — President Obama announced Wednesday that the United States planned to deploy 2,500 Marines in Australia to shore up alliances in Asia, but the move prompted a sharp response from Beijing, which accused Mr. Obama of escalating military tensions in the region. The agreement with Australia amounts to the first long-term expansion of the American military’s presence in the Pacific since the end of the Vietnam War. It comes despite budget cuts facing the Pentagon and an increasingly worried reaction from Chinese leaders, who have argued that the United States is seeking to encircle China militarily and economically.
“It may not be quite appropriate to intensify and expand military alliances and may not be in the interest of countries within this region,” Liu Weimin, a Foreign Ministry spokesman, said in response to the announcement by Mr. Obama and Prime Minister Julia Gillard of Australia.
In an address to the Australian Parliament on Thursday morning, Mr. Obama said he had “made a deliberate and strategic decision — as a Pacific nation, the United States will play a larger and long-term role in shaping this region and its future.”
The president said the moves were not intended to isolate China, but they were an unmistakable sign that the United States had grown warier of its intentions.
China has invested heavily in military modernization and has begun to deploy long-range aircraft and a more able deep-sea naval force, and it has asserted territorial claims to disputed islands that would give it broad sway over oil and gas rights in the East and South China Seas.
While the new military commitment is relatively modest, Mr. Obama has promoted it as the cornerstone of a strategy to confront more directly the challenge posed by China’s rapid advance as an economic and military power. He has also made some progress in creating a new Pacific free-trade zone that would give America’s free-market allies in the region some trading privileges that do not immediately extend to China.
Mr. Obama described the deployment as responding to the wishes of democratic allies in the region, from Japan to India. Some allies have expressed concerns that the United States, facing war fatigue and a slackened economy, will cede its leadership role to China.
The president said budget-cutting in Washington — and the inevitable squeeze on military spending — would not inhibit his ability to follow through. Defense cuts “will not — I repeat, will not — come at the expense of the Asia-Pacific,” he said.
Some analysts in China and elsewhere say they fear that the moves could backfire, risking a cold war-style standoff with China.
“I don’t think they’re going to be very happy,” said Mark Valencia, a Hawaii-based senior researcher at the National Bureau of Asian Research, who said the new policy was months in the making. “I’m not optimistic in the long run as to how this is going to wind up.”
The president is to fly north across the continent to Darwin, a frontier port and military outpost across the Timor Sea from Indonesia, which will be the center of operations for the coming deployment. The first 200 to 250 Marines will arrive next year, with forces rotating in and out and eventually building up to 2,500, the two leaders said.
The United States will not build new bases on the continent, but will use Australian facilities instead. Mr. Obama said that Marines would rotate through for joint training and exercises with Australians, and the American Air Force would have increased access to airfields in the nation’s Northern Territory.
“We’re going to be in a position to more effectively strengthen the security of both of our nations and this region,” he said.
The United States has had military bases and large forces in Japan and South Korea, in the north Pacific, since the end of World War II, but its presence in Southeast Asia was greatly diminished in the early 1990s with the closing of major bases in the Philippines, at Clark Field and Subic Bay. The new arrangement with Australia will restore a substantial American footprint near the South China Sea, a major commercial route — including for American exports — that has been roiled by China’s disputed claims of control.
The United States and other Pacific Rim nations are also negotiating to create a free-trade bloc, the Trans-Pacific Partnership, that would not initially include China, the world’s largest exporter and producer of manufactured goods. The tentative trade agreement was a topic over the weekend in Honolulu, where Mr. Obama hosted the annual Asia-Pacific Economic Cooperation forum, and it will be discussed again later this week when he becomes the first American president to participate in the East Asia Summit meeting, on the Indonesian island of Bali. For China, the week’s developments could suggest both an economic and a military encirclement. Top leaders did not immediately comment on Mr. Obama’s speech, but Mr. Liu, the Foreign Ministry spokesman, emphasized that it was the United States, not China, seeking to use military power to influence events in Asia.
The Global Times, a state-run news organization known for its nationalist and bellicose commentaries, issued a stronger reaction in an editorial, saying that Australia should be cautious about allowing the United States to use bases there to “harm China” and that it risked getting “caught in the cross-fire.”
Analysts say that Chinese leaders have been caught off guard by what they view as an American campaign to stir up discontent in the region. China may have miscalculated in recent years by restating longstanding territorial claims that would give it broad sway over development rights in the South China Sea, they say. But they argue that Beijing has not sought to project military power far beyond its shores, and has repeatedly proposed to resolve territorial disputes through negotiations.
The United States portrays itself as responding to a new Chinese assertiveness in the region that has alarmed core American allies. Secretary of State Hillary Rodham Clinton wrote a recent article in Foreign Policy laying out an expansive case for American involvement in Asia, and Defense Secretary Leon E. Panetta characterized China’s military development as lacking transparency and criticized its assertiveness in the regional waters.
Mr. Obama reached out to China even as he announced the new troop deployment. “The notion that we fear China is mistaken; the notion that we are looking to exclude China is mistaken,” he said.
The president said that China would be welcomed into the new trade pact if Beijing was willing to meet the free-trade standards for membership. But such standards would require China to let its currency rise in value, to better protect foreign producers’ intellectual property rights and to limit or end subsidies to state-owned companies, all of which would require a major overhaul of China’s economic development strategy.
Mr. Obama canceled two previous planned trips to Australia because of domestic demands; he recalled Wednesday at a state dinner that he had visited the country twice as a boy, when his mother was working in Indonesia on development programs.
This time, as president, Mr. Obama arrived at Parliament House to a 21-gun salute and, once inside, to the enthusiastic greeting of Australians crowding the galleries of the vast marble entrance hall.
The two countries have been allies for decades, and cooperated closely in World War II, when there were several dozen American air and naval bases and army camps in the country and Australian combat troops served under American command.
Another purpose of Mr. Obama’s visit is to celebrate those ties. “The United States has no stronger ally,” Mr. Obama said.
Australians fought alongside Americans in every war of the 20th century, and more recently have served in Iraq and Afghanistan.
The war in Afghanistan has become increasingly unpopular here, though, and most Australians want their troops to come home immediately.