A little-noticed item published Sept. 16 by Iran's Fars News Agency reported in 168 words that Iran and Turkey had signed a memorandum of understanding on maritime cooperation. What at first glance might seem a minor news item has, in fact, great potential commercial and military significance, as both countries not only share a land frontier but sit athwart maritime channels that carry significant volumes of the world's seaborne oil where the U.S. Navy is exerting an increasing presence.

Turkish Ports and Maritime Organization Director Hassan Naiboglu and Iranian Ports and Maritime Organization Director Ali Taheri Motlaq signed the MoU, after which Motlaq told reporters, "The value of transited goods between Iran and Turkey is about $8.5 billion. Iran imports $6.5 billion worth of goods and exports about $2 billion to Turkey."

In such a volatile part of the globe, however, the complex interweaving of oil, conflict and U.S. sanctions provided a subtext to the innocuous announcement, as the next day Washington froze all U.S. bank accounts and other financial assets belonging to the Islamic Republic of Iran Shipping Lines and 18 associated companies. Motlaq subsequently informed the Mehr News Agency that IRISL had no assets in the United States subject to impoundment and that the sanctions would have no effect on Iran's shipping activities, particularly since IRISL is on the Paris MoU White List on Port State Control and in good standing in the international shipping community.

The most significant international aspect of last month's confrontation between Russia and Georgia was to focus international attention, albeit briefly, on the question of naval passage into the Black Sea via the 200-mile-long Turkish Straits, which consist of two waterways connected by the landlocked Sea of Marmara. Washington fumed about the naval restrictions imposed by the 1936 Montreux Convention but grudgingly complied as it delivered humanitarian aid on U.S. Navy warships rather than using merchantmen, which are under no such restrictions.

The 17-mile-long Bosporus, which is the Black Sea's sole maritime exit to the Mediterranean, bisects Istanbul and presents significant navigational hazards, as it is only a half-mile wide at its narrowest point at Kandilli. At its southern end the Bosporus empties into the Sea of Marmara, which in turn connects to the 38-mile-long Dardanelles. Under good conditions merchant vessels can pass the Turkish Straits in about 16 hours.

Since the 1991 collapse of the Soviet Union, surging Russian and Caspian oil exports have turned the Turkish Straits into an oil superhighway, much to Ankara's distress, as tankers carrying 2.4 million barrels per day sail the passage every 10 to 15 minutes, weather permitting, 24 hours a day, seven days a week. Prior to last month's hostilities, it was this commercial traffic that concerned Turkey more than warships' passage, but Turkey, which receives nearly two-thirds of its natural gas imports from its giant northern neighbor, is loath to antagonize Moscow by allowing the Pentagon gratuitously to "fly the flag" in Russia's maritime back yard.

Farther east lies the world's most heavily used passage for oil shipments, the Persian Gulf's 21-mile-wide exit into the Arabian Sea, the Strait of Hormuz, whose eastern shore is controlled by Iran. According to the U.S. government's Energy Information Agency, approximately 16.5 million to 17 million bpd of oil is shipped through the Persian Gulf's southern Strait of Hormuz daily.

Both channels have been the site of military clashes -- the Dardanelles since Homer's 8th century B.C. "Iliad" -- but while the last significant military operations in the Turkish Straits occurred during World War I, conflict has roiled the Persian Gulf for the last 30 years, most notably during the 1980-1988 Iran-Iraq war, when tankers sailing the Persian Gulf were subjected to aerial attacks and free-floating mines.

Even worse for commercial shippers operating the approximately 4,000 tankers plying the world's oceans, since Sept. 11, 2001, terrorism has had to be factored into the mix. On Oct. 6, 2002, al-Qaida bombers in a small boat filled with explosives rammed the French tanker Limburg at Mukalla, 354 miles east of Aden, as it was approaching the Ash Shihr Terminal several miles off the Yemeni coast. The attack killed one crewman and spilled 90,000 barrels of oil of the vessel's 397,000-barrel cargo. The U.S. Navy's Maritime Liaison Office in Bahrain subsequently issued an advisory noting, "Shipmasters should exercise extreme caution when transiting ... strategic chokepoints such as the Strait of Hormuz, or Bab el-Mandeb (between Yemen and Djibouti), or ... traditional high-threat areas such as along the Horn of Africa."

For Iran, the ongoing U.S. military operations in the Persian Gulf are part of a larger U.S. agenda to pressure Tehran into abandoning its nuclear energy program, or failing that, launch a military strike.

Secular, democratic Turkey and Iran's mullahs share common maritime interests in both protecting their coasts and promoting their bilateral trade, but the scent of oil is attracting unwanted visitors -- U.S. warships. And, as Homer noted 29 centuries ago, trade and navies are a mix that rarely guarantees peace.