A "low-grade sinus infection" will prevent Barbara Bush from accompanying President Bush on his journey across South America next week, the White House said yesterday.

Daughter Dorothy LeBlond will make the Dec. 2-8 trip to Brazil, Uruguay, Argentina, Chile and Venezuela in her mother's place, spokesman Marlin Fitzwater said.

Mrs. Bush, 65, spent much of the past 12 days on the road with her husband in his travels through Mexico, Europe and the Middle East, including Thanksgiving with American troops in the Saudi desert.

Anna Perez, the First Lady's press secretary, said, "She has a low-grade sinus infection that's irritated by going up and down in airplanes."

Mrs. Bush has been unable to shake the infection, which has bothered her for two to three weeks, Perez said.

The First Lady spent much of October on the road, flying around the country for campaign appearances on behalf of 23 Republican candidates.

LeBlond, 31, a mother of two, is the youngest of the five Bush children and the only daughter. She works for a Washington hospital.

Bush departs Sunday night on an overnight flight to Brasilia, with additional stops in Montevideo and Punta del Este, Uruguay, on Dec. 4; Buenos Aires on Dec. 5; Santiago, Chile, on Dec. 6; and Caracas, Venezuela, on Dec. 7. He is due back at the White House on Saturday night, Dec. 8.