libpq linker problems

I'm having a problem compiling my C program using libpq I have used
the proper linking directories as returned by pg_config both include
and library dirs. I have also used -lpq. Still I get errors

A3.o(.text+0x1e): In function `main':
: undefined reference to `PQconnectdb'
A3.o(.text+0x2c): In function `main':
: undefined reference to `PQstatus'
collect2: ld returned 1 exit status

I have the library installed from the debian package

ldconfig -v | grep pq  libpq.so.3 -> libpq.so.3.1

I'm using libpq-fe.h 

Thank you