[R] plotting circles with symbols()

[eariasca]

Hello,

I am not able to plot a circle of a given radius using symbols().  In  
the example below, the circle appears too large:

plot(0, 0, xlim = c(-1, 1), ylim = c(-1, 1))
symbols(0, 0, circles = 1, inches = FALSE, add = TRUE)

What's happening?

Ery