RESCUE workers were losing hope Thursday of finding a priest who disappeared off the southern coast of Brazil after drifting out to sea four days ago suspended from hundreds of helium-filled party balloons.

Father Adelir Antonio de Carli went missing last Sunday night after he called friends from his mobile phone to say his contraption made of some thousand balloons would soon crash into the Atlantic Ocean.

The chaplain staged the stunt to help raise money for a chapel for truckers in his highway parish.

Brazil's air force suspended its search for de Carli on Thursday, a spokesman said. The navy continued to patrol waters off the coast of Santa Catarina state but was considering halting operations.

"The chances (of survival) are increasingly slim and we are considering when to end the search effort," said Lieutenant Francisco Jose Cavalcante of the navy's southern search unit in Rio Grande do Sul state.

De Carli had left from the southern port of Paranagua and wanted to fly 20 hours due west but winds unexpectedly carried him out to sea in the opposite direction.

Friends and churchgoers have been praying and placing candles at the altar of de Carli's parish church.

Firefighters continued to search beaches and islands off the coast of Santa Catarina state, where they thought the 42-year-old Roman Catholic priest may have washed up.