Canberra, Australia (CNN) -- The United States announced an agreement with Australia Wednesday that will expand military cooperation between the long-time allies and boost America's presence in the region.
The agreement was revealed during a joint news conference between U.S. President Barack Obama and Australian Prime Minister Julia Gillard in the nation's capital, Canberra.
Obama is on a two-day trip to Australia, his first visit as commander-in-chief.
"I am very pleased that we are able to make these announcements here together on Australian soil," Obama said. "Because of these initiatives that are the result of our countries working very closely together as partners, we are going to be in a position to more effectively strengthen the security of both of our nations and this region."
President Obama arrives in Australia Obama stresses Asia-Pacific importance
Under the agreement, up to 250 U.S. Marines will be sent to Darwin and the northern region of Australia for military exercises and training. Over the next several years their numbers are expected to climb to 2,500 -- a full Marine ground task force.
While U.S. officials cited the need to respond to regional natural disasters as a reason for the agreement, concern over China's military expansion is widely acknowledged as a driving factor.
"What we look at is how does our general force posture allow us to protect U.S. interests, protect our allies, and ... secure the region broadly," Deputy National Security Adviser Ben Rhodes told reporters traveling with the president. "China is obviously a piece of the Asia Pacific region, an emerging power."
Rhodes later added that the deal is "part of the U.S. sending a signal that we're going to be present, that we're going to continue to play the role of underpinning security in this part of the region. Part of that context is a rising China."
Analysts note that the deal sends a message to China in a less confrontational way than building up bases closer to Chinese shores.
