New Demands, Behind-Scenes Talks Cloud Trade Pact : Commerce: Backers say much hinges on getting Mexico to agree to protect some U.S. farmers from a flood of imports. Canada elections add uncertainty.

Despite signs of new support in the House of Representatives, the fate of the North American Free Trade Agreement hinges on two uncertain factors: a behind-the-scenes diplomatic struggle with Mexico and the insistence of the new Canadian leader that long-settled elements of the pact must be readdressed.

Little more than two weeks before the House is scheduled to cast its pivotal vote on the trade pact with Mexico and Canada, the White House has launched what Sen. John B. Breaux (D-La.) called “a last-minute blitz” to secure written agreements with Mexico that would protect the United States from a flood of Mexican sugar, citrus products and vegetables--and win the votes of some recalcitrant House members.

But despite feverish negotiations between U.S. Trade Representative Mickey Kantor and Mexican officials, there was no indication that progress was being achieved. One source close to the dispute remained pessimistic about Kantor’s prospects for success.

“If they don’t get those agreements, NAFTA won’t pass,” said Breaux, who supports the trade pact. “If they get the agreements, it will still be very close, but doable.”

The third partner to the agreement is also balking. Jean Chretien, the prime minister-designate as leader of Canada’s Liberal Party, has said he will withhold a proclamation implementing the agreement unless it is modified to protect Canadian energy reserves and deal with unfair subsidies and below-market pricing of imports from Canada’s NAFTA partners.

Administration officials have insisted that there will be no renegotiation of the agreement with Canada. Mark D. Gearan, the White House communications director, said Chretien’s position is “a delicate problem, no doubt about it.”

If approved by simple majorities in the House, which is scheduled to vote on Nov. 17, and the Senate, which would vote shortly afterward, NAFTA would eliminate tariffs and other barriers to commerce among the three countries over the next 15 years. Senate approval is expected, but the House vote is considered too close to call.

At the heart of the agricultural dispute with Mexico is the fear that if limits on Mexican exports of sugar, citrus products and vegetables were removed, as they would be under the trade agreement, the cheaper costs for Mexican farmers would allow them to undercut prices in this country, putting U.S. growers out of business.

U.S. sugar producers regard themselves under threat by a combination of two NAFTA provisions. One would reduce Mexican tariffs that now effectively prevent that country’s soft-drink bottlers from using American corn syrup; the other would remove quotas on Mexican sugar exports to the United States within seven years if Mexico produced more sugar than it consumed for two consecutive years.

Sugar producers in the United States fear that Mexico’s demand for its own sugar would plummet if, under provision No. 1, the Mexican soft drink industry began sweetening its beverages with high-fructose corn syrup.

That would trigger provision No. 2, and exports of Mexican sugar to the United States would quickly bowl over sugar cane growers in Louisiana and Florida and sugar beet farmers in Minnesota, North Dakota and other states in the upper Midwest.

Breaux said that eight to 10 House members from Louisiana, Florida and the sugar-beet states would support the pact only if Mexico agreed to protect U.S. farmers and refinery workers.

The dispute over sugar illustrates the political bind in which President Clinton finds himself.

Clinton is arguing that the agreement would deliver long-range benefits to the nation as a whole by increasing international commerce and boosting exports. But the individual House members whose votes he needs are feeling extreme pressure from their districts based on potentially damaging local impacts.

In the citrus- and vegetable-growing districts of Florida and California, the situation is the same. A senior White House official said the Administration hopes several more House votes could be secured from both states, if new agreements on vegetables and citrus products could be worked out. Failure to reach such agreements, he said, “will be a significant blow, but not necessarily fatal.”

While Breaux said Clinton’s recent push for the agreement had produced “some progress,” leaders of the opposition campaign claim that as many as 208 House members have given public or private commitments to vote against it. That figure is viewed with skepticism by supporters.

Even if all 434 members of the House voted--there is one vacancy--those 208 votes would fall only 10 short of a blocking majority.

Gearan said that there is still “a huge undecided vote out there” and that the Administration is putting on a full-court press to go after each one.

The President is stepping up his public and private activities in the final weeks before the vote. He will begin holding two meetings a day this week with House members, and television appearances on behalf of the trade agreement are being planned.

White House officials say Clinton has made progress in winning the votes of formerly undecided House members from Massachusetts, California and Texas.

But they acknowledge that he is making little or no headway in such Rust Belt states as Ohio, Pennsylvania and Michigan, all strongholds of the organized labor movement, which has vehemently opposed the pact out of concern that it will expose blue-collar workers to stiff competition from lower-wage workers in Mexico.

“I don’t know whether he can do it, but if he wins, it will be by one vote,” said House Majority Leader Richard A. Gephardt (D-Mo.), who plans to deliver several speeches on the House floor this week elaborating his opposition.