Lead your co-worker to take on the issue
As long as your co-worker feels or declares himself to be
unconcerned by the problem, your discussion will not go anywhere. A
sometimes "laborious" initial stage consists in pushing (without
aggression) on his points of resistance so that he sees his
share of the responsibility: In what way is it important for you
that...? What would happen if...?
Hold firm to get responses
If your co-worker doesn't give a real answer, it can be tempting
to do it for him! However, if you let him escape the exchange, he can
retreat into passivity, to "wait and see". The goal of
the meeting: his involvement.
Our natural tendency: to minimize problems and then one day to
explode because they haven't been resolved! It is better, when the
situation becomes intolerable, to say it clearly. Not to
threaten but to express "this is the thing, with respect to …,
that is really serious." We do not try to frighten but on the contrary
to prompt a "realization of responsibility" before it
becomes too late.