Failing to meet an appointment: idiom/saying

Hello,

What is an appropriate way to convey that I will be unable to meet a certain appointment (informal)?

There's some idiom(s) or sayings on the tip of my tongue, but I can't seem to remember them.

I was thinking of the following sentences:

1) 9 PM will be a close call, maybe we can delay the meeting by one hour?

I looked up the idiom close call but all definitions were related to having a brush with a dangerous situation.

2) 9 PM will be a stretch, perhaps we can have the meeting at 10 PM instead?

I couldn't really find an idiom containing stretch that expresses what I want to say. "A bit of a stretch" can mean a mild exaggeration and "requires a stretch of imagination" can mean something is unbelievable...

3) ...

Thank you!