Time Series Prediction Using R CARET

Question

I am new to CARET. I was wondering how this can be used to predict multidimensional time series data.

data(economics)
library(caret)
library(kernlab)

 myTimeControl <- trainControl(method = "timeslice", initialWindow =200,horizon =50, fixedWindow  = TRUE)

svmRbftune <- train(unemploy ~ pce + pop + psavert + uempmed,
                data = economics[1:250,], method = "svmRadial",
                tunelength = 14, trControl = myTimeControl)

svmpredict<-predict(svmRbftune,economics[251:350,])

But then how can we predict one step forward from here