DUBLIN (Reuters) - The Brexit agreement on the Irish border that assures Northern Ireland will remain aligned with the European Union s customs union and single market  puts a floor  under what is possible in negotiations on trade after Britain leaves the EU, Ireland s foreign minister said.  What it means is any deal that is done has to be better than the default position, otherwise we won t be able to agree it,  Simon Coveney told national broadcaster RTE after the deal was struck early on Friday.  I think what that does is, it puts a floor under what is possible in terms of the outcome that we can t fall below, so Ireland obviously has a huge interest in the phase two negotiations.  