Phrases Offering and Refusing Help

I'm sorry, but I'm not able to assist you at this moment.

Meaning

I cannot help you right now due to circumstances.

Translation language

John: 'I need help with this urgent task.'
Alice: '<b>I'm sorry, but I'm not able to assist you at this moment.</b> I have a prior commitment.'
John: '<b>I'm sorry, but I'm not able to assist you at this moment.</b> I'm swamped with deadlines.'
Alice: 'Could you review my presentation?'