Secretary of State
The official said the 71-year-old former senator is eager to rejoin the talks in person before negotiators reach their self-imposed deadline of June 30 to wrap up a comprehensive accord.
"When he needs to be there, he will be there," the official, who spoke on condition of anonymity to discuss the talks, said in a conference call with reporters.
Kerry, who has led the U.S. team in the grueling seven-country negotiations, broke his femur and damaged a replacement hip when he fell off his bicycle in France on May 31.
His hospitalization in Boston is longer than usual for a broken limb, and State Department officials have declined to predict when he will be released. He has worked on the Iran talks and other high-priority diplomatic issues by phone, officials said.
The United States and five other world powers are negotiating with Iran in an effort to produce a deal that would ease economic sanctions on Iran if it accepts restrictions aimed at preventing it from obtaining a nuclear weapon.
Diplomats and private experts say the landmark agreement is likely to be completed, though some tough issues are still undecided.
The senior administration official hinted that U.S. officials would not object if the talks run a few days past June 30.
The official said the group's provisional agreements with Iran don't specify a deadline, and noted that the diplomatic bloc missed a target date of March 31 for a preliminary nuclear agreement. That deal emerged several days later.
"I think everybody thought that was well worth it," the official said.
Top Iranian officials have recently insisted that they would never allow nuclear inspectors to enter their military bases, and would never permit interviews of Iranian scientists.
But the U.S. official insisted that such seeming "red lines" aren't obstacles to an agreement.
Lower-level technical experts for the seven countries have met daily in Vienna, and diplomats have joined them with increasing frequency.
It's expected that foreign ministers, including Kerry, will join the group for the final days of talks, as they did in March, though no precise schedule has been released.
The five permanent members of the United Nations Security Council -- England, France, Russia, China and the United States -- as well as Germany, are negotiating with Iran.