MEXICO CITY, FEB. 26 -- The Mexican Finance Ministry appeared Thursday night to be attempting to lower expectations about the financial impact of the nation's debt-for-securities swap.

The ministry said the importance of the exchange of U.S. Treasury-backed bonds for a portion of its foreign debt at a discount is less the "quantitative" impact on the debt than the fact that creditors "are formally recognizing for the first time that there is a difference between the book value of the Mexican debt and its market value."

Mexico this year "will present other options and proposals for reducing the foreign debt ... on the basis of a recognition of debtors' and creditors' joint responsibility for a solution to the problem," the ministry said in a statement.

Jose Angel Gurria, Mexico's director of public credit and chief foreign debt negotiator, will stay in New York until all the bond bids from creditors are processed by Morgan Guaranty Trust Co., Mexico's agent for the auction, a ministry spokesman said.

The spokesman, Roberto Contreras, said there will be no announcement about the outcome of the auction until Gurria consults with senior officials here next week.

Mexico is expected to reject bids that do not offer the government at least a 25 percent reduction in the value of the debts that would be exchanged for the bonds, analysts said.

The deadline for submitting bids was this afternoon. Mexico has been given up to a week to study the offers and will announce results by next Friday at the latest, the ministry said.

The U.S. Treasury has authorized Mexico's purchase of up to $10 billion in U.S. zero-coupon bonds to back the Mexican bonds offered at the auction.

Some Mexican officials have expressed concern that the bond plan's potential may have been unduly exaggerated by its U.S. backers in New York and Washington when it was first disclosed in December. Morgan Guaranty suggested at the time that the bonds would be traded for debt at a 50 percent discount, retiring as much as $20 billion of the total $52 billion in Mexican government debts eligible for the exchange.

Expectations now are that the bond trade will retire less than $10 billion in debts, reducing Mexico's interest bill by several hundred million dollars at most, analysts said. By way of comparison, a one-point rise in dollar interest rates would increase Mexico's debt servicing costs by nearly $1 billion this year.

The bond deal is being concluded at a critical time for Mexico's government.

Next week marks the beginning of the second stage of a controversial new anti-inflation program begun in December, a plan that calls for the monthly indexing of wages to anticipated consumer price increases.

Inflation is now running at about 170 percent and Mexico's powerful government-affiliated unions are demanding wage increases large enough to compensate for lost purchasing power.

In 1987, the country's biggest union federation noted in a report this week, labor was granted five wage increases for a cumulative 106 percent pay increase, but they failed to keep pace with last year's 159 percent rate of inflation.

Labor's local organizational machinery is considered essential to the ruling party's success in the July 6 presidential election, a contest that promises to be the most difficult the government has faced in a generation.

If there is a perception in local political circles that the zero-coupon plan failed to alleviate Mexico's debt servicing burden significantly, observers believe the government will be pressured to introduce new initiatives to cut payments before July.

Acknowledging the popular support for bolder moves toward debt relief, ruling party presidential candidate Carlos Salinas de Gortari has proclaimed from the stump repeatedly in recent weeks that "without economic growth, there can be no servicing of the foreign debt."