After meeting throughout the day on Tuesday, Kerry and Iranian Foreign Minister Mohammad Javad Zarif were back at the negotiating table for a third consecutive day in the town overlooking Lake Geneva in the Swiss canton of Vaud.
Kerry did not watch the speech of Israeli Prime Minister Benjamin Netanyahu to the US Congress, as in a twist of fate he was thousands of miles away in the middle of negotiations for the very deal which the Israeli leader denounced as a grave danger to his country.
Despite the political drama, US officials have shrugged off Netanyahu's Tuesday address.
"I am not focused in the politics of this," US President Barack Obama said.
"I am not focused on the theatre," Obama said.
"As far as I can tell, there was nothing new.
"On the core issue, which is how to prevent Iran from obtaining a nuclear weapon which would make it far more dangerous, the prime minister did not offer any viable alternatives."
Kerry was due to fly later on Wednesday to Riyadh where he will meet with Gulf Cooperation Council foreign ministers, as well as new Saudi King Salman.
Saudi Arabia has been wary about the growing rapprochement between its ally the US and its regional foe, Shiite Muslim Iran.
But US officials said that even if there is a deal with Iran, that does not mean they will turn a blind eye to the other activities of the country, still
branded by Washington as the number one state sponsor of terrorism.
"If we have an agreement on the nuclear file, our view is that that is something that will contribute directly to regional stability, as well as global security and stability," a senior State Department official told reporters.
But he warned "regardless of what happens with the nuclear file, we will continue to confront aggressively Iranian expansion in the region, Iranian aggressiveness in the region."