The United States intends to send three nuclear-powered warships -- which also can carry nuclear weapons -- into the Australian port of Freemantle near Perth this week despite the possibility of demonstrations there, administration officials said yesterday.

The ships are the aircraft carrier USS Enterprise and guided missile cruisers USS Arkansas and USS Truxtun. New Zealand has banned such ships from its ports, raising questions about the viability of the ANZUS defense treaty between Australia, New Zealand and the United States.

Last month, the Sydney Peace Squadron organized a demonstration to protest nuclear-armed ships visiting Australian ports. Sailors aboard the destroyer USS Joseph Strauss had to use fire hoses to keep antinuclear protesters on small boats clear of their ship when it was berthed in Sydney.

The Reagan administration is trying to keep Australia from catching what diplomats term the "New Zealand disease." Laurence W. Lane Jr., U.S. ambassador to Australia, has said that the United States could not heed New Zealand's ban on nuclear-armed ships without encouraging Australia to follow suit.

In retaliation for the ban, the United States has canceled some intelligence sharing and joint military exercises with New Zealand. Australian Prime Minister Robert Hawke supports the ANZUS treaty and the U.S. position that American warships, nuclear or conventional, must have access to the ports of its treaty partners.

However, the left wing of Hawke's Labor Party is pressing for a ban on ships powered by nuclear reactors and equipped to carry nuclear weapons.