Auto.arima with xreg in R, restriction on forecast periods

Question

I am using the forecast package and implement auto.arima with xreg. Here I want to forecast only for 1 year ahead but I am unable to use h parameter in the forecast function. Below is the reason for that:

Definition is given in manual(F1 check):

h = "Number of period of forecast but if xreg is used 'h' is ignored and the forecast period will be number of rows"

Please suggest me an alternate way to use h for the specific period forecast.