Back at work only days after an 18-day negotiating marathon to seal the unprecedented accord, Kerry met Saudi Foreign Minister Adel al-Jubeir, the beginning of a charm offensive designed to win over the many doubters in the United States and abroad.
"All of us in the region want to see a peaceful resolution to Iran's nuclear program," Jubeir said after their talks.
He welcomed a deal with a "robust and continuous inspections regime to make sure Iran does not violate the terms of the agreement," adding it should also have an effective and quick "snapback" mechanism that allows for sanctions to be quickly reimposed if Tehran violates Tuesday's accord.
"We hope that the Iranians will use this deal in order to improve the economic situation in Iran and to improve the lot of the Iranian people, and not use it for adventures in the region," Jubeir said.
But he warned "if Iran should try to cause mischief in the region we're committed to confront it resolutely.