[R] axis labels disappear

[Angel Lopez]

When I do a plot, e.g.
plot(1:10)
and resize the window so that the x-axis becomes too small to hold all 
the x-axis labels, R automatically makes some of the labels disappear so 
that the remaining fit in the available space.
I would like to be able to tell R which labels should not be removed.

I've tried plotting the axis with axis() but this behaviour is still there.
plot(1:10,xaxt="n")
axis(side=1,at=1:10,labels=c("1","","","","5","","","","","10"))

In my case when I resize the window first the "10" disappears and the 
the "5". Also if I start the graph with a 'small' window (e.g. 
X11(width=3,height=3) I do not get the "10".
Is there a way to force that these labels are not removed automatically?

I've searched the documentation but couldn't find any reference, Could 
anyone point me to the right documentation for this feature?
Thanks
Angel