The competition watchdog has given interim authorisation of Qantas' alliance with Emirates.

The Australian Competition and Consumer Commission's (ACCC) ruling on Thursday allows the two airlines to begin preparations for their proposed tie-up, ahead of a final ruling from the ACCC expected in March.

"The ACCC is allowing Qantas and Emirates to start implementing their alliance because of the long lead time required to market and sell tickets before the commencement of long-haul services," ACCC chairman Rod Sims said in a statement.

The proposed alliance involves an extensive codesharing arrangement, reciprocal frequent-flyer benefits and joint marketing, pricing and coordination on certain routes between the two carriers.

It is regarded as a key plank of Qantas chief executive Alan Joyce's plan to turn around the airline's struggling international arm, which lost $450 million in 2011/12.