aborting a merge

Let's say I do a propagate from a main branch to a development branch.
I get dumped into emacs merge to sort things out.
Let's further say the emacs merge gets too hairy.  I need to do 
the merge more slowly with other tools, or perhaps start the merge 
over again, with more insight.

How do I get out of emacs merge mode without letting monotone 
think the merge has been completed?

I want to get back to the unmerged state so I can proceed with 
the complicated step-by-step merge tools exquisitely explained in 
the manual.

-- hendrik