The Moscow Treaty signed with great fanfare by US President George Bush and his Russian counterpart Vladimir Putin in May 2002 calls on both sides to reduce their strategic nuclear warheads to between 1700 and 2200 by 2012.

But it refers to "operationally deployed" weapons, essentially offering both governments a loophole that allows them to move an unlimited number of warheads into storage and keep them indefinitely under lock and key.

While US officials have praised this option, the remarks by Under Secretary of Energy Linton Brooks before the Senate Sub-committee on Strategic Forces represented the first official indication that the Bush administration had actually decided to exercise it.

"The 2012 nuclear stockpile will be substantially reduced from current levels," Brooks told lawmakers on Wednesday. "But reduction will not lower the stockpile to 1700-2200 total warheads."

The retained warheads will be needed for routine maintenance of the arsenal and for replacing damaged bombs "to meet commitments to allies"and to address threats that may arise in the future.

"If confirmed, it is extremely serious for the security of the world and further indicates a policy of 'do as we say and not do as we do' towards weapons of mass destruction pursued by Washington," said Dan Plesch, an international arms control expert.