Cruise was in the country to promote the film on the popular "Wetten Dass ... (I'll Bet ...)" TV show. He said on the show Saturday that two pilots were at the ready to fly him home should Holmes go into labor.
"If Katie calls, I'm gone," the 43-year-old actor said.
Holmes, 27, is in the final stages of her pregnancy with the couple's first child.
Cruise confirmed to Bild in Monday's editions that he and Holmes plan to wed in the coming months. They have been engaged since June.
"First the baby, then the film," he was quoted as saying. "Then, in summer, we want to get married. I won't let this woman get away."
"Mission: Impossible III" will be released May 5.