Australia, the major supplier of foreign food to Iran, is sending signals to the White House that it would be reluctant to comply with any U.S. call for a food boycott of Iran should current economic and diplomatic sanctions fail to secure the release of the U.S. hostages.

Informed observers believe Prime Minister Malcolm Fraser has conveyed to U.S. Ambassador Philip Alston Australia's deep doubts about the wisdom of a ban on exporting food to Iran.

Together with New Zealand, which shares Australia's views, Australia is the most important supplier of food to Iran, which imports 30 percent of its food. The Iranians currently are buying about $200 million worth of live sheep and frozen meat from Australia annually.

[In Washington, a U.S. official said, "We've asked only for implementation of the sanctions in the U.N. resolution vetoed by the Soviet Union, which specifically exempted food and medicine. We have no intention at the present time of changing our policy regarding food and medicine."]

Australia has so far been quick to accede to Carter's requests for retaliatory measures against Iran. This week it joined the European Common Market in agreeing to ban all nonfood trade after May 17 if there is not substantial progress on the hostage question.

Also, Australia has announced it will not appoint a new ambassador to Tehran -- the last ambassador completed his term two months ago and has returned to Canberra. It has withdrawn its trade commissioner from Iran, banned the export of any military equipment to Iran (which mainly affected a small company here making rifle targets) and cancelled export incentives and government insurance for nonfood exports from Australia to Iran.

At a cabinet meeting five days ago, senior ministers also agreed in principle that the government would grant any further "reasonable" request from the United States. The sticking point has been food exports.

This week, Australia adopted the May 17 deadline for a total ban on all but food and medical exports. At the same time, the government ordered that no new contracts in nonfood exports be entered into. In effect, the Australian government has cancelled upwards of $50 million in nonfood and medicine trade a year.

The food trade has been increasing at the rate of 25 percent a year and is now of major importance to the politically influential sheep and cattle growers. Fraser himself is a millionaire farmer specializing in beef cattle, and four other senior members of his cabinet are either sheep or cattle ranchers.

Australia is concerned that a food ban would be counterproductive, raising the question of the morality of such retaliation when none of America's friends and allies doubt the immorality of keeping the hostages incarcerated in Iran.

The powerful farming interests -- the junior partner in Fraser's Conservative coalition is the rural National Country Party -- also fear that even one food embargo, however much Iran may be at fault, would damage Australia's reputation as a reliable supplier.

So far, however, Australia's bitterly opposed major political parties have been in rare bipartisan agreement in support of U.S. policy in Iran in the wake of the aborted attempt to rescue the American hostages.

It marks the first time since World War II that the right-wing Liberal Party led by Malcolm Fraser and the Socialist Labor Party led by Bill Hayden have been in firm-agreement on a major question of foreign policy.