Generating the necessary heat and pressure is already possible. The problem is keeping the whole process stable over long periods while getting more usable ener

Generating the necessary heat and pressure is already possible. The problem is keeping the whole process stable over long periods while getting more usable energy out of the fusion than is needed to maintain it, if I remember correctly the experiments so far had extremely short durations. Apparently Iter was designed to make sure the energy balance works out, but we'll see.