The first contingent of U.S. Marines sent to Australia in April has completed its deployment.

The initial company-sized rotational deployments of 200-250 Marines to Australia's Northern Territory city of Darwin are to continue through 2013.

The Australian Ministry of Defense said in its "Social and Economic Assessments" of the U.S. deployment, the regional social effects will be minimal while there will be a modest regional economic benefit associated with deployment.

The findings were included in an Australian Ministry of Defense news release Thursday outlining remarks by Australian Minister for Defense Stephen Smith and Minister for Defense Science and Personnel Warren Snowdon.

The Social Assessment found that the rotations of Marines through the Northern Territory would have no indigenous effects on the local demands for housing, infrastructure or social services either in the Northern Territory, along with a "negligible" impact on the environment.

In the last several years, the United States and Australia have deepened defense contacts.

The Economic Assessment said that Marine deployments are predicted to inject roughly $1.8 million into the local economy this year, an amount increasing to $2.3 million in 2013, primarily via the region's hospitality, retail and transport sectors.

Smith said that the Australian government's next step is to determine the likely effects of a projected much larger eventual force of up to 1,100 Marines in northern Australia, as the number of U.S. Marines scheduled to rotate through northern Australia is to reach 2,500 annually within the next several years.

Smith said the social assessment had found the rotations would have no effect on the demand for housing, infrastructure or social services in the Northern Territory and a negligible impact on the environment.

"The social and economic assessments also identified a range of risks and opportunities which have been assessed and are not considered to require urgent or significant action at this time," he said.

"The next assessment process will involve community polling, public forums and public submissions and is expected to commence later this year."

Bolstering the deployment on Wednesday U.S. Deputy Secretary of Defense Ashton Carter gave a speech to the National Bureau of Asian Research on Washington's Pacific redeployment.

"Our political and military rebalance to the Asia-Pacific region is one of the most important tenets of the new strategy," Carter said. "There are several, this is the most important.

"Underlying our security engagement with the region is our support for long-standing principles that go well beyond security -- of free and open access to commerce; of a just international order that upholds the rule of law; of open access to all domains; and of the peaceful resolution of disputes."

Carter said that in addition to the 2,500 Marines on rotation in Australia, the United States will have four Littoral Combat Ships stationed in Singapore.