Alonso also defended his compatriots from accusations of racism after former McLaren team mate Lewis Hamilton suffered abuse from spectators earlier this month at the Circuit de Catalunya.
"We are pretty far behind," Alonso was quoted as saying on As newspaper's Web site.
"We are not in a position to fight for anything important right now.
"Thinking about a podium (in Melbourne) would be too optimistic at the moment... today, thinking about it coldly, getting on the podium is a dream."
"We are not in a position to fight for anything important right now."
Alonso said Ferrari were ahead, with McLaren and BMW Sauber close behind, while Renault were fighting in the next group with Williams and Red Bull.
"But everything changes very quickly in Formula One," added Alonso.
"Two or three weeks ago BMW were a little bit behind, we were close to them. Now they are very close to McLaren.
"They (BMW) are going very fast. They have not shown their cards. They are running with the tank full and are doing very good times."
Racing against racism
Alonso was also critical of International Automobile Federation (FIA) plans to launch a 'Racing Against Racism' campaign at the Spanish Grand Prix in April.
"This is not a racist country nor are the supporters," he said.
"It was an isolated case and if the FIA or whoever says Spanish fans are racist, it's laughable.
"Last year they called me a dog at some races. (Former champion) Niki Lauda said things about me and nobody said anything nor came to show me their support either," added the Spaniard, who said he had not spoken to Hamilton since the incident.
FIA, Formula One's governing body, has warned Spanish circuits they risk heavy sanctions if there is any recurrence of the abuse witnessed at the Circuit de Catalunya.
Hamilton, Formula One's first black driver and runner-up last year in an astonishing rookie season, will be testing at the Spanish track again next week.