Question

I am sorry, I am unable to accompany you begin (I regret my)​

Answer 1

Answer: I regret my not being able to accompany you.

Explanation:

Answer 2

The sentence starting with given words is as follows

I regret my inability to accompany you.

To convert the sentence the adjective unable will change into noun inability.

The word "regret" is a verb in the sentence. It means to feel sad or disappointed over non-completion of the task.

The statement in the question conveys the message that the person is apologising for not accompanying the person, he promised to.