SPOKANE, Wash. (AP) _ Reverberations of the gunfire in the Persian Gulf are being felt by many U.S. farmers, who are facing yet another trade embargo after a foreign invasion.

Iraq's attack on Kuwait prompted President Bush to order economic sanctions that ended sales of U.S. commodities such as wheat, rice and tobacco to the Middle Eastern nation.

Moreover, disruption of oil supplies from the warring countries has caused the costs of fuel to run tractors and for petroleum-based fertilizers to climb higher. So farmers' costs could be going up at the same time the embargo depresses prices.

Paul Drazek, international trade specialist for the American Farm Bureau Federation in Washington, said the loss of sales to Iraq and Kuwait would be small, compared with total U.S. farm exports.

''It's not a big chunk of the action but it will have some impact on producers. In agriculture, even a small amount can have an impact on prices,'' Drazek said.

The U.S. Agriculture Department estimated agricultural sales to Iraq in 1989 at $720 million, out of total farm exports of $40 billion - or 1.8 percent. Sales were even smaller to Kuwait.

Still, Drazek and others said they feared the administration's sanctions would be costly to American farmers.

''The worst thing to do is single out agriculture. You're signaling the world that you're using food as a weapon,'' he said. ''We're saying we support the president's action as long as it is across the board and not singling out agriculture.''

Wheat growers said they hoped the economic sanctions do not bring about a repeat of President Jimmy Carter's embargo in 1980 that cut off sales to the Soviet Union after that country's invasion of Afghanistan.

''Sanctions operations, particularly related to food products, usually don't work very well,'' said Nelson Denlinger, executive vice president of U.S. Wheat Associates, a Washington, D.C., cooperative organization that represents wheat producers.

''As with the Afghan invasion, you'll find that commodities of that sort are replaceable,'' he said. ''You usually will find somebody, somewhere, who will sell you something. Food is not a good weapon for changing another country's behavior.''

''It's a never-ending challenge to figure out what kind of rhubarb is going to happen next that will affect the ability to market wheat,'' said John Oades of U.S. Wheat Associates office at Portland, Ore. ''It's a very politically vulnerable commodity.''

Middle Eastern oil is another politically sensitive commodity, said Carl Schwensen, executive vice president of the National Association of Wheat Growers in Washington, D.C.

''We're removing a significant source of petroleum imports from our consumption picture,'' he said. ''As prices increase, that will flow through to the farmer as higher fuel, chemical and fertilizer costs.''

The increasing petroleum costs come at a time when the price of a bushel of wheat is falling because of a large crop of 2.7 million bushels, up 700,000 bushels from last year, Schwensen and others said.

In July, the average farm price for wheat was $2.81 a bushel, down from $3.78 during the same month a year ago.

Iraq last year bought 1.3 million tons of wheat from the United States.

Other agricultural commodities also get pinched by the embargo.

Iraq has been the U.S. rice market's largest customer, accounting for as much as one-fourth of U.S. exports.

Almost all of the exports to Iraq - about 350,000 to 450,000 tons a year - is long-grain rice grown in Arkansas, Louisiana, Texas and Mississippi.

''I think it will cause less sales for Arkansas rice, which in effect will hurt our economy and hurt our farmers,'' said John Tull, a Lonoke, Ark., rice farmer. ''And I think that next year we will probably have to have a reduction in rice acres.''

''Our farmers are seriously affected, and we would hope that agriculture and rice would be treated in a separate way from political things,'' said Jim Willis, vice president for foreign market development at the Houston-based Council for Market Development.

Earlier this year, the Bush administration decided not to extend to Iraq additional credit guarantees. Iraq had purchased U.S. rice through the use of about $1 billion a year in government credit guarantees.

Iraq is an importer of U.S. tobacco products, said Britt Cobb, an assistant director of marketing for the North Carolina Department of Agriculture. Iraq in 1988 imported $21 million of American tobacco, he said.

California agriculture exports to Iraq totaled a little less than $4.4 million in 1989, a little more than 1 percent of the state's total food and fiber exports, according to statistics compiled by California State World Export Commission. Cotton and livestock comprise the bulk of that total.

Chicken growers also will feel the impact of the invasion, said Tommy Irvin, Commissioner of Agriculture for Georgia, a major exporter.

During the first four months of 1990, the United States sold more than $3 million worth of pieces of chicken, 900 metric tons, to Kuwait and about 106 metric tons of whole chicken valued at $130,000, Irvin said.