A senior government official said for the first time that President Augusto Pinochet will not run in 1989 elections, and opposition groups dismissed the Chilean leader's threat to nullify the results of a recent plebiscite that denied him a new term.

Interior Minister Carlos Caceres, who heads the Cabinet and is in charge of Chile's domestic policy, said in an interview published Sunday by the El Mercurio newspaper that Chile is seeing the "final chapter" of the Pinochet presidency.Voters on Oct. 5 rejected Pinochet's request for another eight-year presidential term. The plebiscite rejection means Pinochet, 72, must leave the presidency in March 1990. A new election is now set for December 1989.

El Mercurio quoted Caceres as saying Pinochet "will not be a candidate in the December 1989 election. ... The political constitution does not contemplate the re-election of the candidate after the plebiscite."

It was the first clear statement from a top government official on Pinochet's political future.

After the plebiscite, the opposition called for talks with the military government to reform the constitution on the grounds that a 1980 vote approving the document was flawed and gave the armed forces too much power in a civilian government.

But Pinochet warned Saturday that the opposition must declare its support for the 1980 constitution. If not, he said, "this will annul the plebiscite."

The Chilean leader had warned several times before that the opposition would "have to abide by the consequences" if it continues to insist on constitutional changes.