I regret to inform you that your contract will not be renewed.
WORD CHOICE: WORD CHOICE: regret, be sorryRegret is very formal when it is used to apologize• I deeply regret causing you offence.It is more usual to say you are sorry• I'm sorry if I hurt your feelings.If you regret doing something, you wish you had not done it• Do you regret resigning from your job? • I asked him to join us, then regretted it. You can say you are sorryabout something that you wish you had not done, or something that is not your fault• I was sorry that she decided not to come back.You can say that you are sorry to say something or regret tosay something before giving bad news• I am sorry to tell you that you failed the test.• We regret to inform you that no trains will run today.
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.