WASHINGTON -- Backed by powerful agricultural interests, conservative Republican senators are leading an effort to lift restrictions on the sale of food, agricultural and medical products to Cuba and other nations hostile to the United States.

Although a similar bill failed to clear its first hurdle in a House committee in May, supporters of the Senate proposal say the momentum for change is growing. They cite the financial incentive of selling food to banned markets as an important reason.

Supporters of the legislation, which could come up for a Senate vote later this month, say support among some of the more conservative sectors of the U.S. economy reflects growing exasperation with the government's inclination to resort to economic sanctions as a cheap and easy instrument of foreign policy.

U.S. farmers argue that sanctions are not really cheap because they place more and more regions of the world off-limits to U.S. agricultural sales. They have not been mollified by Clinton administration attempts to allow limited sales to off-limits countries.

Dean Kleckner, president of the American Farm Bureau, visited Cuba with 19 other members in May. On their return, he testified at a Senate hearing that ``any action such as the embargo or sanction does long-term harm to farmers and the agricultural economy.

``I was struck by the Castro regime's oppressive effect on the Cuban economy and the lack of impact U.S. sanctions have had on this tiny island in ending Castro's influence,'' Kleckner said. ``U.S. unilateral sanctions on trade with Cuba have now been in effect for more than three decades and what do we have to show for it?''

In an attempt to aid their farm constituencies, Sens. Richard Lugar, R-Ind., Chuck Hagel, R-Neb., and John Ashcroft, R-Mo., introduced legislation this year exempting agricultural sales from U.S. restrictions on trade with hostile countries.

The Republicans have worked out differences between their bills and hope to attach an amendment called ``Food and Medicine to the World'' to the agriculture spending bill when Congress returns from its July 4 break.

The bill would allow nations on the State Department's terrorist list, including Cuba and Iran, Libya, Sudan and North Korea, to purchase food and medicine. But such sales would not be eligible for government credits or guarantees. Iraq would not be affected because it is under multilateral sanctions, which the bill does not address.

Sales to countries at war with the United States would be banned and no nation under U.S. sanctions would be able to buy fertilizer from U.S. producers, presumably because it could be used to make explosives.

Other efforts to create exceptions to the U.S. trade embargo have floundered, largely because they emphasized only the humanitarian aspect.

Unlike a similar bill sponsored by Sen. Chris Dodd, D-Conn., which is expected to have less support because it focuses narrowly on Cuba, the legislation sponsored by farm state Republicans is likely to frame the debate in terms of hard cash.

Echoing Kleckner, the Farm Bureau president, the lawmakers say agricultural sales to Cuba could reach $1 billion a year. They have also identified Iran as a good prospective market for U.S. grain.

Because of its faltering agriculture economy, hard hit by the loss of Soviet subsidies, Cuba is forced to buy more food from abroad every year. In 1998, Cuba bought about $800 million in imported food, mostly from Canada and Europe, the government says.

Helms holding his ground

Sen. Jesse Helms, R-N.C., who has long opposed any lifting of sanctions against Cuba, tried to stop the farmers' legislative assault on the embargo by proposing a compromise that would allow only those sales licensed by the Treasury Department.

However, the compromise does not appear to be gaining political support and has angered Cuban-American Reps. Lincoln Diaz-Balart, R-Fla., Ileana Ros-Lehtinen, R-Fla., and Bob Menendez, D-N.J. who steadfastly oppose any crack in the embargo.

Yet the Cuban-American lawmakers know they are swimming against a strong current. An aide to Diaz-Balart said, ``We are aware that there's a new alliance, but he's going to stand his ground.''

The Cuban American National Foundation, in a recent statement, said that ``rather than helping the Cuban people, unconditional food sales to the Castro regime will only succeed in strengthening Castro's ability to control the Cuban population.''

The Clinton administration also opposes the unrestricted sale of food and medicine to unfriendly nations. Undersecretary of State Stuart Eizenstat has said that food sales ``do not generally enhance a nation's military capabilities or support terrorism,'' but he claimed the legislation proposed by Ashcroft, Hagel and Lugar would weaken the President's ability to influence troublesome nations through the threat of severe economic sanctions.

Bill fails in House

The aide to Diaz-Balart said Congress' Cuban-American lawmakers will try to stop the movement toward the easing of sanctions in the House, where a food and medicine bill failed in the Appropriations Committee on a 24-28 vote in May, thanks largely to the efforts of Rep. Tom DeLay of Texas, the Republican whip.

But the president of the Farm Bureau -- which came out against the embargo on Cuba in January after years of silence on the issue -- predicted momentum for change will sweep aside opposition to opening new markets to America's farmers.

``Like the Dutch boy with his finger in the dike, you can't hold it back forever,'' Kleckner said.