Disclosing consideration for funded Master's during PhD program admissions

As an undergraduate in the admissions process for a PhD program, should I disclose my status as a finalist for a prestigious fellowship that would fund a Master's program after being offered admission to a PhD program?

If so, when is the appropriate and responsible time to disclose this information?

Importantly, if I were to receive the MA fellowship, I would certainly accept due to its prestige.

My concerns are two-fold:

1) I do not wish to lessen my bargaining power by disclosing this information too early in the admissions process (i.e. during negotiations over PhD funding).

2) I do not wish to provoke the ire of admissions boards and department faculties by withholding this information until too far into the admissions process.

In terms of a timeline, notification for MA fellowship recipients will be made between March and late April.