FACTBOX-Energy supplies at stake if Iran is attacked

(Reuters) - Iran has refused to halt its nuclear programme despite the threat from major powers of increased U.N. sanctions.

The United States said on Sunday that Tehran had left the U.N. Security Council no choice but to increase sanctions after Iran ignored an informal deadline to respond to an offer for talks on its nuclear programme.

The West accuses Iran of seeking to build atomic weapons, a charge Tehran denies.

The U.S. says it wants a diplomatic solution to the dispute but has not ruled out military action if that fails.

Iran, pumping around 4 million barrels per day (bpd) of oil, is the second largest producer in the Organization of the Petroleum Exporting Countries (OPEC). Iran's output is over 4 percent of global oil supply. It exports around 2.5 million bpd.

OPEC's Secretary General Abdullah al-Badri said in July it would be impossible to replace Iran's oil output in the case of disruption due to an attack.

GULF OIL EXPORTS

- The biggest concern to oil markets is that 40 percent of the world's traded oil sails on tankers through the narrow Strait of Hormuz off Iran's southern coast.

Iran has threatened to impose controls on shipping there if attacked and warned Gulf neighbours of reprisals if they play any role in such an attack. The U.S. Navy has said it would not allow Iran to block the route.

The International Energy Agency estimated in July 2008 that more than 15 million barrels per day of oil passed through the strait.

The following are estimated crude exports through the strait by country of origin:

COUNTRY Millions barrels crude per day*

Saudi Arabia 6.0

Iran 2.5

United Arab Emirates 2.3

Kuwait 1.7