write a gzip file from data frame

I'm trying to write a data frame to a gzip file but having problems.

Here's my code example:

df1 <- data.frame(id = seq(1,10,1), var1 = runif(10), var2 = runif(10))

gz1 <- gzfile("df1.gz","w" )
writeLines(df1)

Error in writeLines(df1) : invalid 'text' argument

Any suggestions?

EDIT: an example line of the character vector I'm trying to write is:

0 | var1:1.5 var2:.55 var7:1250

The class label / y-variable is separated from the x-vars by a " | " and variable names are separated from values by " : " and spaces between variables.

EDIT2: I apologize for the wording / format of the question but here are the results: Old method:

system.time(write(out1, file="out1.txt"))
#    user  system elapsed 
#   9.772  17.205  86.860 

New Method:

writeGzFile <- function(){
  gz1 = gzfile("df1.gz","w");
  write(out1, gz1);
  close(gz1) 
}

system.time( writeGzFile())
#    user  system elapsed 
#   2.312   0.000   2.478 

Thank you all very much for helping me figure this out.