A senior administration official on Friday said the list has been replaced with a smaller roster of 28 countries with troops in Iraq.
The quiet downsizing of the list took place sometime after the June transfer of power to an interim Iraqi government.
The official, however, could not say why the administration did away with the original list.
The original list consisted of 30 countries that publicly offered support to the Iraq invasion and another 15 that did not want to be named as part of the group.
Former member Costa Rica withdrew last September under pressure from voters who opposed the government's decision to back the invasion.
The United States, backed by allies including Britain and Italy, invaded Iraq in March 2003 on the premise that the oil-rich country posed a grave threat because it possessed weapons of mass destruction.
No such weapons have been found and the Bush administration acknowledged earlier this month that it had abandoned the search for them.