I have serious reservations about this.

Meaning

I have strong doubts or concerns about this.

Examples

• John: 'I think we should proceed with the merger.'<br>
• Alice: '<b>I have serious reservations about this.</b> We need more due diligence.'
• John: '<b>I have serious reservations about this.</b> It's not adequately tested.'
• Alice: 'They want us to launch the product next month.'<br>