From a press release issued by FIM:

Road Racing World Championship Grand Prix

2004 Japanese Grand Prix in Motegi

The Suzuka Circuit has established a long-term programme of works including various modifications aiming at improving the circuit, principally the safety in view of the Grand Prix counting towards the Road Racing World Championship Grand Prix. This programme of modifications to improve safety has been discussed at length with the Grand Prix Safety Commission. These modifications, however, cannot be carried out before the Grand Prix originally scheduled in April next. For this reason, an agreement has been reached according to which the 2004 Japanese Grand Prix, originally scheduled on 4 April next, will not take place on the circuit of Suzuka.

The FIM created the Grand Prix Safety Commission last May. The role of this Grand Prix Safety Commission is to work on improving the safety around the Road Racing World Championship Grand Prix circuits, following the evolution of Grand Prix racing in recent years, and particularly due to a recent technical evolution which includes an increase in performances of the new MotoGP motorcycles. In this aspect, the FIM requested the MSMA (Motorcycle Sport Manufacturers’ Association) to review the technical regulations taking into account the general performances and behaviour of the racing motorcycles and its consequences on safety.

Regarding the 2005 Japanese Grand Prix, the circuit of Suzuka and the FIM will keep on the discussions in an effort to organise this Grand Prix again as the season opener on the circuit of Suzuka.

Moreover, in agreement with the FIM and Dorna, the Grand Prix scheduled on the circuit of Twin Ring Motegi on 19 September 2004 will bear the title of Japanese Grand Prix.