I'm afraid I'm tied up then.

Meaning

I'm busy at that time.

Examples

• John: 'Can you make it to the meeting on Friday?'
• Alice: '<b>I'm afraid I'm tied up then</b>. How about Monday?'
• John: '<b>I'm afraid I'm tied up then</b>; I have a prior engagement.'
• Alice: 'Would you be free for lunch tomorrow?'