The UK is doing nothing to force the EU to do anything.
So, why are we talking about a hard border? Is it nothing to do with the UK leaving the EU?
Additionally imposing a hard border between Northern Ireland and the rest of the UK is just as unworkable as imposing one between the Republic of Ireland and Northern Ireland.
Therefore the only option is for the ROI, NI and GB to be in the same customs union. That means either the UK will have to stay in the single market, or Ireland will have to leave the EU. AFAIK, there is little appetite for Ireland to leave the EU, meaning that the former is the only option.