FACTBOX: The Strait of Hormuz, Iran and the risk

(Reuters) - Here are some facts about the Strait of Hormuz, the sea channel which flows along Iran's coastline at the entrance to the Gulf. It is the world's most important waterway because of the huge volume of oil exported through it.

-- Oil flows through the Strait account for roughly 40 percent of all globally traded oil supply, according to the U.S. Energy Information Administration (EIA). The figure fluctuates with changing OPEC output.

-- In May 2007, the International Energy Agency (IEA) estimated 13.4 million barrels per day (bpd) of crude passed through the narrow channel on tankers.

-- An additional 2 million barrels of oil products, including fuel oil, are exported through the passage daily, as well as liquefied natural gas (LNG).

-- Exports from the world's largest LNG exporter Qatar also pass through the Strait en route to Asia and Europe, totaling some 31 million tonnes a year.

-- Ninety percent of oil exported from Gulf producers is carried on oil tankers through the Strait.

-- One of U.S. Central Command's (CENTCOM) key missions in the Gulf is to ensure the free flow of oil and energy supplies.

-- Between 1984 and 1987, a "Tanker War" took place between Iran and Iraq, where each nation fired on the other's oil tankers bound for their respective ports. Foreign-flagged vessels were caught in the crossfire.

-- Shipping in the Gulf dropped by 25 percent because of the exchange, forcing the intervention of the United States to secure the shipping lanes.

-- Iran has admitted to deploying anti-aircraft and anti-ship missiles on Abu Musa, an island strategically located near the Strait's shipping lanes.

-- The EIA predicts oil exports passing through the strait will double to between 30 million and 34 million bpd by 2020.

-- Over 75 percent of Japan's oil passes through the Strait.

-- Merchant ships carrying grains, iron ore, sugar, perishables and containers full of finished goods also pass through the strategic sea corridor en route to Gulf countries and major ports like Dubai.

-- Heavy amour and military supplies for the U.S. armed forces in Iraq and other Gulf countries pass through the channel aboard U.S. Navy-owned, U.S.-flagged and foreign-flagged ships.

-- Geographic location: a narrow bend of water separating Oman and Iran connects biggest Gulf oil producers like Saudi Arabia with the Gulf of Oman and the Arabian Sea.

-- At its narrowest point, the Strait is only 34 miles (55 km) across.