Ronald is talking with Anthony. All of a sudden, Kenneth runs over here and says
"sorry to interrupt, the boss just gave a job to Anthony which is quite urgent"
"sorry for interrupting, ..."
which one should Kenneth say?
Ngram Viewer shows both are common.
What are the differences between "sorry to keep you waiting" and "sorry for keeping you waiting."? gives a nuanced difference in context. How about the example of Kenneth?