The strongest endorsements came from regional mediators and European governments, which described the breakthrough as a major step toward restoring stability in the Middle East and preventing further escalation.
Qatar's Prime Minister welcomed the memorandum of understanding reached between Tehran and Washington and voiced support for the next phase of negotiations.
Doha has played a central role in diplomatic efforts throughout the conflict and was among the key countries involved in mediation.
UN Secretary-General António Guterres congratulated both sides for reaching what he described as a peace deal providing for "an immediate and permanent ceasefire, the reopening of the Strait of Hormuz, as well as a framework for further negotiations."
"This represents a critical step towards the peaceful settlement of the conflict," Guterres said, while thanking Pakistan, Qatar, Egypt, Saudi Arabia, Türkiye and other regional countries for helping facilitate the agreement.
British Prime Minister Keir Starmer also welcomed the deal, saying London stood ready to support the technical negotiations that will now begin.
"I warmly welcome today's agreement reached between the United States and Iran," Starmer said, reiterating Britain's longstanding position that Iran must never acquire a nuclear weapon.
Japan's Prime Minister Sanae Takaichi also welcomed the announcement, expressing hope that "free and safe navigation through the Strait of Hormuz will be ensured in practice, and that a final agreement on Iran's nuclear issue and other matters will be reached as soon as possible."
In a joint statement, Britain, France, Germany and Italy signaled their readiness to ease sanctions on Iran in response to steps addressing its nuclear program.
"Iran must never acquire a nuclear weapon. We stand ready to work with the US, Iran and the IAEA to this end," the four countries said.
The international reaction followed announcements by Iranian and US officials that they had reached a memorandum of understanding ending hostilities and launching a 60-day period of negotiations on a final settlement.
Tehran has said final negotiations will begin only after implementation of key provisions in the framework agreement, including the lifting of the maritime blockade and the release of Iranian funds.
US President Donald Trump described the agreement as a historic achievement, saying it would bring "peace and security" to the region and allow for the reopening of the Strait of Hormuz, one of the world's most important energy shipping routes.
While many details remain unresolved, the broad international backing suggests governments across the region and beyond are eager to see the fragile agreement evolve into a lasting settlement.
