"'The Speaker of the House just called and she was very concerned about the president: She wants to make sure we have control of the nuclear weapons," Hyten told a podcast at the Atlantic Council.
"I told her we always have control of the nuclear weapons," Hyten said.
Hyten was being questioned on a media report on Friday from Bob Woodward and Robert Costa new book "Peril" that revealed Milley had phoned his Chinese counterpart Gen. Li Zuocheng on January 6 to assure him that the United States was not planning to declare war or to attack China.
"For the people listening, you should be absolutely 100% confident that we always have control of the nuclear weapons and there's always a very disciplined process in place by the Joint Staff," Hyten added.
Hyten said the January 8 conversation between Milley and Li had been agreed on January 1 and was part of "routine" communications between the top US and Chinese military leaders.
He described it as "just normal business" for the chairman of the joint chiefs.