How to suppress async messages for background jobs

[Francesco Montorsi]

Hi,
  when using & at the end of a command, bash prints messages like:

  frm@genius:~$ kwrite &
=>[1] 20986
  frm@genius:~$
=>[1]+  Done                    kwrite
  frm@genius:~$

is there a way to tell bash not to print those lines marked with => ?
I could not find any command searching in the bash manual or googling...

Thanks,
Francesco