regexp with sed again!!!

Shell Programming and Scripting
1

please help:

I want to add 1 space between string and numbers:
input file:
abcd12345
output file:
abcd 1234

The following sed command does not work:

sed 's/\([a-z]+\)\([0-9]+\)/\1 \2/' file

Any ideas, please

Andy

2 
$ echo abcd12345 | sed 's/\([a-z]\{1,\}\)\([0-9]\{1,\}\)/\1 \2/'
abcd 12345
$ echo abcd12345 | sed "s/[0-9]/ &/"
abcd 12345

Extended regular expression operators are not available in sed

3

can for for this also..

shameer