unix command to insert double quotes

Hi, I am looking for a unix command which inserts double quotes around all values in a text file. For example,

Input:
1234 200 4686 3506056
9646 457 5647 5066762
5656 366 5869 5978459

Output:
"1234" "200" "4686" "3506056"
"9646" "457" "5647" "5066762"
"5656" "366" "5869" "5978459"

Please somebody give me a hint. Thanks!

awk ' { for(i=1;i<=NF;++i) $i="\""$i"\"";print $0 }' file

or

sed 's/\([^ ]*\)/"\1"/g' file

Thanks a lot anbu23 ! It works fine.