Kerry, 71, broke his leg while cycling in France on Sunday, after an intense round of negotiations with his Iranian counterpart Mohammad Javad Zarif the previous day, and is being flown home to Boston on a U.S. military aircraft.

Saturday's six hours of talks in Geneva were expected to be Kerry and Zarif's last face-to-face meeting until at least mid-June, U.S. officials said, ahead of an end-June deadline to agree a deal to curb Iran's nuclear program in exchange for sanctions relief.

Asked if Kerry expected to be back in the negotiating room by the end of the month, State Department spokeswoman Marie Harf replied: "Yes, absolutely."

Kerry, for whom an Iran deal would be a legacy-defining achievement, has taken a lead role in the complex seven-nation talks, logging multiple trips to Europe and often holding marathon one-on-one talks with Zarif.

Expert-level talks are continuing and the lead U.S. negotiator, Wendy Sherman, is expected to rejoin them this week. Despite his condition, Kerry made telephone calls on Sunday and Monday to Obama and the foreign ministers of Iran, France and Spain.

If the White House wanted to pull in another senior official, which current and former officials said was highly unlikely, it has two obvious understudies at hand: Kerry's former deputy, Bill Burns, and his current deputy, Antony Blinken.

One medical specialist, who is not involved in Kerry's treatment, said the former presidential nominee faced surgery and a minimum healing time of six to eight weeks with his weight off the leg, though he could be up and about on crutches a day after surgery.