Jason Clare said four more ships and three aircraft were on the way to aid the search for survivors from the boat carrying an estimated 210 people. A number of Australian defence and civilian vessels are already in the area.
"We are still in the critical window where more lives can be saved. The advice I have is that the water temperature is about 29 degrees. People can survive for up to 36 hours if they have lifejackets or they have debris to hold onto," Clare said.
So far 110 people have been rescued and three bodies have been recovered, he said.
On Thursday Western, Australian police commissioner Karl O`Callaghan told local television that 75 people were feared drowned.
"A large number of survivors have been pulled from the water and are being taken on board a Defence vessel and a number of civilian vessels to Christmas Island," Australia`s Customs and Border Protection said in a statement.
"Australian authorities on the Island are preparing to receive passengers from early this morning."
Refugees seeking asylum in Australia often set sail from Indonesia heading for Australia`s Indian Ocean territory of Christmas Island in dangerous and overcrowded boats, with the help of people smugglers.
So far this year, more than 50 boats carrying more than 4,000 asylum seekers have been detected by Australian authorities.
As many as 200 died when an overcrowded boat sank off the coast of East Java in December, 2011. (*)