In this paper, we address the problem of designing a distributed application meant to run both classical and asynchronous iterations. MPI libraries are very popular and widely used in the scientific community, however asynchronous iterative methods raise non-negligible difficulties about the efficient management of communication requests and buffers. Moreover, a convergence detection issue is introduced, which requires the implementation of one of the various state-of-the-art termination methods, which are not necessarily highly reliable for most computational environments. We propose here an MPI-based communication library which handles all these issues in a non-intrusive manner, providing a unique interface for implementing both classical and asynchronous iterations. Few details are highlighted about our approach to achieve best communication rates and ensure accurate convergence detection. Experimental results on two supercomputers confirmed the low overhead communication costs introduced, and the effectiveness of our library.