Convergence issues with nlme:lme

Dear list

Having tried to fit a mixed effects model with nlme:lme, and found
convergence problems, how do we inspect the fitted model object to find out
what is the problem?

Reproducible example:

set.seed(3)
data <- data.frame(y = rnorm(100), x = rnorm(100), group = rep(1:10, each

= 10))

model <- lme(y ~ x, random = ~ 1 + x | group, data = data)

Error in lme.formula(y ~ x, random = ~1 + x | group, data = data) :
  nlminb problem, convergence error code = 1
  message = iteration limit reached without convergence (10)

Now that we have the model object, how do we interrogate it to find out
what went wrong? I need to do this in code, so I won't have access to the
Error message raised when the model was first fitted (unless there is a
magical way to get at the error (which I haven't yet found)

Thanks !