How to remove duplicate occurrences at the end of a string using Regex in C#?

Question

Regular Expressions

Very simple question, but I'm not strong in regular expressions.
There is a string s1 and you need to delete all occurrences of the substring s2 in it, if they are in a row from the end.
For example:

s1 = "qwertyuiop asdfghjkl zxcvbnm abc abc abc";
s2 = " abc";
// в результате должно пулучиться "qwertyuiop asdfghjkl zxcvbnm"

I have this function made by recursion, but I would like to have a more elegant solution on regular expressions.