[texhax] plain TeX: how to center text within a \item environment?

[Rodolfo Medina]

In plain TeX, I wish to have something like:

\item{bla} bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla
\item{bla} bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla
\item{bla} bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla
                                       <a centered text>
\item{bla} bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla
\item{bla} bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla bla

, but to be centered with respect to the `\itemed' line, which is shorter than
normal line.

How can I achieve that?

Thanks for any help
Rodolfo