Can't connect to postgresql using 'psql -d database -U user -W'

Hello,

I have a problem with postgresql 7.4 installed on Linux Ubuntu 5.04
(hoary).

I made an 'alter' command for my db users :

eg: alter user postgres with password 'postgres';
ALTER USER

but I can't connect to postgresql using :

tobini% psql -d template1 -U postgres -W
password: postgres
psql: FATAL:  IDENT authentication failed for user "postgres"

Do you have an idea about this problem ?

Thanks.

C. Tobini