(Joanna Stern / ABC News)

Rancho Palos Verdes, Calif. - "Designed by Apple in Cupertino, Assembled in China." That's what it says on the back of the iPhone right now.

But Tim Cook wishes it could say "Assembled in the United States."

Speaking at the All Things D conference in Los Angeles, the Apple CEO said, "I want there to be a product made in the United States." Cook was responding to a question by interviewer Walt Mossberg about the issues Apple faces with manufacturing overseas and why it doesn't attempt to make an iPhone in the United States.

Cook highlighted the issues with manufacturing in the United States - cost and facilities - but also noted that parts of the iPhone are made in Apple's home country. "The glass on your iPhone is made in a plant in Kentucky," Cook said on stage. Additionally he said that "the engine for the iPad and iPhone are built in the U.S. in Austin."

Apple has faced criticism about working conditions at its Foxconn factory in China. ABC News' Nightline exclusively reported on those conditions in February.  In March, Foxconn and Apple agreed to improve the conditions, including worker pay and hours, after the Fair Labor Association made a series of recommendations.

Cook detailed the challenges with manufacturing in the United States, including the lack of processor production in the country. Still, when asked if one day it might say "assembled in the United States on an iPhone," he responded by saying, "It may, it may. But you could put down there several parts are made in the United States."