The "deal" we're talking about - but anyone using that word has no right to call themself a journalist - is a withdrawal agreement. Just that, and nothing more.
And that's the easy part, remember. Withdrawal agreement. Could have done that at any time in the last two years.
That's what Article 50 is for: Complete a withdrawal agreement
The problem is what it's always been. Theresa May wants a new treaty out of this process, and she's not going to get one.
She is terrified of finding herself in the position of no legal right to a new treaty, and entirely dependant on the will and whim of the European Union.
but they will never accept the obligation.
Unable to leave because of Ireland. unable to force a new treaty.