Problem linkint with libpq

I'm trying to compile a small c program that integrates with PostgreSQL,
but when I get to link the prog i get the following error.

/tmp/ccFrRISc.o: In function `main':
/tmp/ccFrRISc.o(.text+0x57): undefined reference to `PQsetdbLogin'

I'm doing this on FreeBSD 4.3 and PostgreSQL is 7.1.2

I made this prog to determin that what causes the problem:

#include </usr/local/include/pgsql/libpq-fe.h>

int main (void) { char *pghost,   *pgport,   *pgoptions,   *pgtty,*dbUser,*dbPassword; char *dbName; int nFields; int
i,j; PGconn *conn;
 
 pghost = "localhost"; pgport = "5432"; pgoptions = NULL; pgtty = NULL; dbName = "monitor"; dbUser = "username";
dbPassword= "donttell";
 
 conn = PQsetdbLogin(pghost, pgport, pgoptions, pgtty, dbName, dbUser,
dbPassword); return(0);
}

\Flemming