The United States will release 30 million barrels of crude from its strategic reserves, part of a plan by the International Energy Agency to coordinate the release of 60 million barrels of oil from its member countries.
Concerns that disruptions to Libya's oil supply could slow the global economic recovery prompted the release. Soaring gasoline prices and calls from U.S. lawmakers have put the Obama administration under pressure to tap the stocks.
The U.S. strategic petroleum reserve, the world's largest emergency oil stockpile, was created by Congress after the 1973-74 Arab oil embargo.
It holds 727 million barrels of crude oil in underground salt caverns at four sites along the Texas and Louisiana coast.
The stockpile was initially designed to be used only during a severe supply disruption. But Congress recently modified the law governing the stockpile so it could also be used if a supply disruption caused a major increase in petroleum prices that threatened the U.S. economy.
The following are the oil sales and loans made by the U.S. government from the reserve:
* Sept 2005 Hurricane Katrina - Sold 11 million barrels.
* 1996-97 Nonemergency sales - Sold 28.1 million barrels (5.1 million in Weeks Island sale to pay for decommissioning of storage site and transfer of its oil; 12.8 million to reduce the federal budget deficit; 10.2 million to pay for the cost of operating the SPR).
* 1990-91 Iraqi invasion of Kuwait - Sold 21 million barrels (3.9 million in Oct 1990 test sale; 17.2 million in Jan 1991 drawdown ordered by president).
* Nov 1985 Test sale - Sold 967,000 barrels.
* Sept 2008 - Loaned 5.4 million barrels of crude to five oil companies after hurricanes Gustav and Ike cut supplies.
* June 2006 - Loaned 750,000 barrels of sour crude to ConocoPhillips and Citgo after the Calcasieu Ship Channel closed and deliveries stopped to Louisiana refineries.
* Jan 2006 - Loaned 767,000 barrels of sour crude to Total Petrochemicals USA after the Sabine Neches ship channel closed and deliveries stopped to Texas refineries.
* Sept/Oct 2005 - Loaned 9.8 million barrels of sweet and sour crude after Hurricane Katrina disrupted Gulf of Mexico production and damaged terminals, pipelines and refineries.
* Sept 2004 - Loaned 5.4 million barrels of sweet crude due to disruptions in the Gulf of Mexico caused by Hurricane Ivan.
* Oct 2002 - Loaned 98,000 barrels to Shell's Capline Pipeline to keep storage tanks full to withstand Hurricane Lili's winds.
* Oct 2000 - Loaned 30 million barrels to boost winter heating oil supplies in the Northeast.
* Aug 2000 - Exchanged 2.8 million barrels of crude oil for 2 million barrels of heating oil to create Northeast Home Heating Oil Reserve.
* June 2000 - Loaned 500,000 barrels each to Citgo and Conoco, after the Calcasieu Ship Channel closed and blocked crude oil shipments to Louisiana refineries.
* Dec 1998 to Feb 2000 - Exchanged 11 million barrels of lower-quality heavy crude in SPR with Mexico's PEMEX for 8.5 million barrels of higher-quality sweet crude more suitable for U.S. refineries.
* April 1996 - Loaned 900,000 barrels of SPR crude to ARCO after company's pipeline to Cushing, Oklahoma, had blockage.
(Reporting by Tom Doggett and Emily Stephenson; Editing by Lisa Shumaker)