compiling on debian does not find a valid PostgreSQL 8.4+ installati

Hi,
in order to check an updated Italian translation, I would like to
compile pgadmin3 on my Debian box. This is what happens:

giuseppe(at)scarafaggio:~/src/cvs/pgadmin3$ ./configure --prefix=/usr/local/pgadmin3-1.14
checking build system type... i686-pc-linux-gnu
checking host system type... i686-pc-linux-gnu
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
[...]
checking for PQexec in -lpq... no
checking for PQconninfoParse in -lpq... no
checking for krb5_free_principal in -lpq... no
checking libpq-fe.h usability... yes
checking libpq-fe.h presence... yes
checking for libpq-fe.h... yes
checking PostgreSQL in /usr... failed
configure: error: you must specify a valid PostgreSQL 8.4+ installation with --with-pgsql=DIR

I really do not understand what the problem is. I do have all packages
for 8.4 and 9.0 installed, as shown here:

Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Nome Versione Descrizione
+++-===============================-===============================-==============================================================================
ii postgresql-8.4 8.4.8-2 object-relational SQL database, version 8.4 server
ii postgresql-9.0 9.0.4-1+b1 object-relational SQL database, version 9.0 server
ii postgresql-client-8.4 8.4.8-2 front-end programs for PostgreSQL 8.4
ii postgresql-client-9.0 9.0.4-1+b1 front-end programs for PostgreSQL 9.0
ii postgresql-client-common 119 manager for multiple PostgreSQL client versions
ii postgresql-common 119 PostgreSQL database-cluster manager
ii postgresql-contrib 9.0.4-1 additional facilities for PostgreSQL (supported version)
ii postgresql-contrib-8.4 8.4.8-2 additional facilities for PostgreSQL
ii postgresql-contrib-9.0 9.0.4-1+b1 additional facilities for PostgreSQL
ii postgresql-doc 9.0.4-1 documentation for the PostgreSQL database management system
ii postgresql-doc-9.0 9.0.4-1 documentation for the PostgreSQL database management system

Do you have any idea and what should I do?

Thanks,
Giuseppe