CAIRO -- The emir of Qatar, on a visit to Iran, referred to the Arab Gulf. Iran's president was quick to correct him: It's the Persian Gulf, he said.
The flap over the name of the body of water that separates Qatar and Iran reflected the deep and growing disquiet among Iran's Arab neighbors over Tehran's nuclear ambitions.
Arab diplomats said the emir, who is a US ally, went to Iran last week on a delicate diplomatic mission and with a private message: President Mahmoud Ahmadinejad needed to cool his rhetoric and cooperate with the international community.
The hard-line Iranian leader showed his distaste for the message in a goodbye ceremony -- pointedly reported Wednesday by Tehran radio -- with a hard jab, suggesting the Qatari leader was a Western lackey.
Iran takes pride that the Gulf is widely known by the country's ancient name, Persia, but Arabs bridle. They are eager to point out that six Arab countries, but only one Persian land, border the strategically important sea through which much of the world's oil supply must pass.
Attempting diplomatic niceties as he was saying goodbye, the emir, Sheik Hamad bin-Khalifa al-Thani, congratulated his host on Iran's fine soccer team and said he hoped it would bring pride to all the ''Arab Persian Gulf" region during the 2006 World Cup in Germany.
Ahmadinejad shot back: ''I believe you called it the Persian Gulf when you studied in school," he said in a pointed reference to the emir's education at Sandhurst Military Academy in England, once the colonial ruler of much of the Arab world.
Seemingly unfazed, the emir fired Monday's final volley: ''By the way, the Gulf belongs to all."
Since Ahmadinejad's election last summer, Tehran's relations have significantly cooled with its oil- and gas-rich neighbors and are far chillier than in the days of his predecessor, Mohammad Khatami, who promoted dialogue and close ties with Arab neighbors.
Most anxious are Arab countries that lie on the east side of the Arabian Peninsula, across the water from Iran. They are loosely joined in a political and economic alliance known as the Gulf Cooperation Council, and have begun expressing fears that Ahmadinejad could go too far in his strident drive for a nuclear program and Iranian nationalism.
They worry about deadly pollution should Iran suffer a nuclear accident and about possible Iranian retaliation against American military bases in Kuwait, Qatar, and Bahrain should the United States launch a preemptive strike. Other economic and political heavyweights in the group include Saudi Arabia, the world's largest oil producer, the United Arab Emirates, and Oman.
A sign of the unease showed itself in a front-page editorial this week in Kuwait's Al-Siyassah daily. Iran, it said, was engaged in a ''boyish politics." The newspaper further declared that the Americans have the right to ''guarantee the security of the [region's] oil fields . . . and oil's export routes."
Kuwaitis, who allow the Americans to use their country as a forward supply base for the war in Iraq and from which the war was launched, owe the United States a deep debt for having driven Saddam Hussein's soldiers from the oil-rich country in 1991.
But Arab fears stretch beyond Iranian accidents or retaliation. There is anxiety about possible civil strife between their ruling Sunni Muslim majorities and Shi'ite minorities.