Any military action in the Strait of Hormuz in the Gulf would knock out oil exports from OPEC's biggest producers, cut off the oil supply to Japan and South Korea and knock the booming economies of Gulf states.

Here are some key facts on what passes through the international waterway and some of the direct economic consequences of any attack on merchant shipping.

-- 2.9 billion deadweight tons passes through the strait every year.

-- Crude oil exported through the Strait rose to 750 million tons in 2006.

-- 27 percent of transits carry crude on oil tankers, rising to 50 percent if petroleum products, natural gas and Liquefied Petroleum Gas transits are included.

-- Transits for dry commodities like grains, iron ore and cement account for 22 percent of transits.

-- Container trade accounts for 20 percent of transits, carrying finished goods to Gulf countries.

Oil exports passing through Hormuz (2006 figures)

Saudi Arabia -- 88 percent

Iran -- 90 percent

Iraq -- 98 percent

UAE -- 99 percent

Kuwait -- 100 percent

Qatar -- 100 percent

Top 10 importers of crude oil through Hormuz (2006 figures)

Japan -- Takes 26 percent of crude oil moving through the strait (shipments meet 85 percent of country's oil needs)

Republic of Korea -- 14 percent (meets 72 percent of oil needs)

United States -- 14 percent (meets 18 percent of oil needs)

India -- 12 percent (meets 65 percent of oil needs)

Egypt -- 8 percent (N.B. most transhipped to other countries)

China -- 8 percent (meets 34 percent of oil needs)

Singapore -- 7 percent

Taiwan -- 5 percent

Thailand -- 3 percent

Netherlands -- 3 percent (Source: Lloyd's Marine Intelligence Unit)