When you have to talk to someone about a serious, and maybe uncomfortable, topic, it's good to start by saying:

Can I talk to you?

This phrase alerts the listener that you're not just making small talk; you have something serious about. Here are some examples of conversations that you may want to start by saying "Can I talk to you?":

• You need to reprimand one of your employees for doing something wrong.
• You just got some bad news, and you need to share it with your partner.
• You're going to break up with the person you've been dating.

If you want to make this expression a little bit less serious (but still pretty serious), add "for a minute" or "for a second".

To make it more formal, use "May I", "speak with", and "for a moment" instead:

Jessica, may I speak with you for just a moment?