The US government is working on it as well. The Gateway Station is meant to be used for the moon and where they assemble the Mars ship. 2028, iirc, is when they will build the mars ship and then do a year or two long test voyage in cislunar space. The reason for waiting until 2031 for the Mars mission is because NASA will get a free return trajectory to Earth for the Mars mission, increasing safety on the first one.

I cannot speak for other nations, really.