Calling an MPI-based C program in R

Hello,
 
I currently work on the development of an R package where most of the
algorithm is implemented in C.
I would like to use MPI to improve the speed of the C routines when used
in a distributed computing environment. I am very new to MPI.

From what I found in the R archive and online, I came to the conclusion

that packages like Rmpi provide an interface to MPI so that R users can
use capabilities of distributed computing at the R level. 
However, I would like to use the capabilities of MPI at the C level and
use R as the interface to the C routine.
 
Could anyone tell me if it is possible in the latest version of R to
call a C program which itself relies on calls to the MPI library? If it
is, could you please refer me to some documentation?
 
Thank you.
 
Romain