merging two vectors

Dear R users,

It may be very simple but it is being difficult for me.
I have two vectors with some common string. And, i want to combine  
into a vector in such a way that it includes string from both  
vectors and make a unique.

For example:

x <- paste(rep("A",5),1:5,sep = ".")
x
[1] "A.1" "A.2" "A.3" "A.4" "A.5"

y <- paste(rep("A"),3:7, sep = ".")
y
[1] "A.3" "A.4" "A.5" "A.6" "A.7"

Now, I want to combine these two vectors in the following way:

"A.1" "A.2" "A.3" "A.4" "A.5"  "A.6" "A.7"

I tried with merge(), but not able to get as I want.