Disclosing consideration for funded Master's during PhD program admissions
If we're talking about a program such as a Marshall or Fulbright scholarship, such awards are usually considered sufficient grounds to postpone enrollment while the fellowship is being pursued.

On the other hand, I wouldn't raise this possibility until it becomes an actual issue. You're introducing unnecessary obstacles in the admissions process that way. If an offer comes along from a school or one of these fellowships, you can deal with it then