Try this
- Name the confirmed part and the missing fact separately.
- Say when you expect to learn more, if known, and offer a clear point at which the other person can make an independent plan instead of waiting indefinitely.
A worked example
“I’d like to see you Thursday, but I cannot confirm the time yet.”
An invented example to adapt, not a real exchange or a script you have to follow.
Before you leave it here
Name when you expect to know more, and avoid asking the other person to hold unlimited time.