From a press release issued by the FIM:

The Grand Prix Permanent Bureau met yesterday at the FIM Headquarters in Mies and decided
the following :

For 2004, the Regulations remain unchanged. In the MotoGP class, upon unanimous request from the Manufacturers members of MSMA, the fuel tank capacity allowed remains fixed at 24 litres for the 2004 season. As from 2005, it will be reduced to 22 litres.