  The action principle of the BF type introduced by Capovilla, Montesinos,
Prieto, and Rojas (CMPR) which describes general relativity with Immirzi
parameter is modified in order to allow the inclusion of the cosmological
constant. The resulting action principle is on the same footing as the original
Plebanski action in the sense that the equations of motion coming from the new
action principle are equivalent to the Holst action principle plus a
cosmological constant without the need of imposing additional restrictions on
the fields. We consider this result a relevant step towards the coupling of
matter fields to gravity in the framework of the CMPR action principle.
