U.S. Secretary of State John Kerry broke his leg in a bicycle crash Sunday after striking a curb, and scrapped the rest of a four-nation trip that included an international conference on combating the Islamic State group.

Kerry was in stable condition and in good spirits as he prepared to return to Boston for further treatment with the doctor who previously operated on his hip, U.S. State Department spokesman John Kirby said. He said X-rays at a Swiss hospital confirmed that Kerry fractured his right femur.

Kerry, 71, was taken by helicopter to Geneva’s main medical center, HUG, after hitting a curb with his bike near Scionzier, France, about 40 kilometers southeast of the Swiss border.

Paramedics and a physician were on the scene with his motorcade at the time and provided him immediate attention. They quickly decided to order the 10-minute-long helicopter transport.

Kerry had been in Geneva for six hours of meetings with Iranian Foreign Minister Mohammad Javad Zarif on Saturday as the sides now work to seal a comprehensive accord by June 30.

The prospect of a lengthy rehabilitation could hamper the nuclear talks and other diplomatic endeavors. Even if Kerry does not need surgery, it was not immediately known when he could fly again after returning to the United States.

Kerry has been the lead negotiator in several marathon sessions with Iran going back to 2013. The injury could affect other potential trips, such as one to the Cuban capital to raise the flag at a restored U.S. Embassy.

As for the current trip, Kerry had planned to travel to Madrid on Sunday for meetings with Spain’s king and prime minister, before spending two days in Paris for an international gathering to combat IS.

Report compiled with information from Associated Press.