The troops are there on a six-month rotational basis and will take part in training exercises with the Australian Defence Force.
The two countries are boosting defence ties, with the US eventually deploying a 2,500-strong force in northern Australia by 2017.
The move has irked Beijing but US and Australian leaders have stressed it is not an attempt to contain China.
Welcoming the troops, Australia’s Defence Minister Stephen Smith said the decision to host them was a response to a changing global balance.
This is the first time the United States has committed to a permanent rotation of its forces through Australia.
In military terms the deployment is modest, but the presence of US troops in yet another Pacific location is being seen by many as a sign of Washington’s realignment of its strategic forces to meet the growing presence of China.
With US bases already in South Korea, Japan, Guam and elsewhere, the Chinese have questioned the need for more American forces across the Pacific and say they feel encircled.
The Washington Post report said that the two countries were planning ”a major expansion of military ties”, including plans for drone flights from the Cocos Islands – a pair of coral atolls in the Indian Ocean north-west of Australia.