The announced agreement between world powers and Iran over its nuclear program on Tuesday provoked sharp reactions across the Arab world, with some cheering the success of diplomacy and others fearing it would empower Iran and increase instability.
The deal added a new, unpredictable factor to a region where many major players are closely allied with either Shiite Iran or Sunni Saudi Arabia, and any gain by one is seen as a strategic loss by the other.
While the United States has long been closer to the Saudi camp, the great effort the Obama administration put into reaching the accord left many feeling it had abandoned its traditional allies in a way that could shift the balance of power in the region.
Saudi Arabia and its regional allies see Iran as the ultimate source of much of the region’s violence, pointing to its deep support for President Bashar al-Assad in Syria, Hezbollah in Lebanon, Shiite militias in Iraq and Houthi rebels in Yemen.
In its haste to reach an agreement, many Saudis say, the United States effectively ignored Iran’s destructive policies.
“Iran is an aggressor,” said Jamal Khashoggi, a veteran Saudi journalist who has advised government officials. “It has ambitions and plans that it is implementing in the region, and it is using force, not diplomacy, in the region.”
His fear, shared by many of Iran’s enemies, was that sanctions relief for Iran would give it greater resources to fund its militant proxies.
“Iran under sanctions was a pain in the neck for the Saudis, and it will be more of a pain in the neck without sanctions,” he said. “There is no sign that the Iranians are going to change and bring peace.”

While most members of its alliance are Shiite, Iran has also supported Palestinian groups like Hamas and Islamic Jihad, which are Sunni.
And it has spent years investing in proxy forces such as Hezbollah in Lebanon and Shiite militias in Iraq, groups whose rallies are punctuated by chants of “Death to America!”

The New York Times, Beirut, 14 July 2015