DOHA, Qatar — Persian Gulf monarchies issued a cautious endorsement on Monday of the accord Secretary of State John Kerry negotiated last month to constrain Iran’s nuclear program.

“This was the best option among other options,” said Khalid al-Attiyah, the foreign minister of Qatar, who hosted a meeting of the Gulf Cooperation Council that Mr. Kerry attended.

In a news conference with Mr. Kerry, Mr. Attiyah said the secretary of state had repeated his assurance that the United States would stop Iran from acquiring a nuclear weapon if Tehran failed to adhere to the accord.

“We are confident that what they undertook makes this region safer and more stable,” he added.

Mr. Kerry and his counterparts from the Persian Gulf states also agreed on ways to expedite the military support and training efforts that President Obama promised at a meeting in May at Camp David with senior gulf state officials.