From the United web-site.

United 1K:
"When you fly 100,000 paid miles or 100 paid segments on United Airlines in a calendar year, you attain Premier Executive 1K® membership in the United Airlines Mileage Plus® program. Your qualifying, paid flight miles earned on Star Alliance™ member flights also count toward Premier status."

The last sentence is a little vague. Do Star Alliance flights only count toward the 100K mile requirement or the 100 segment requirement too?

If so, GREAT! Early next year, I may just do this! Probably "just" 25 round-trips!