The long-awaited showdown vote on the postal privatization bills that could determine the fate of Prime Minister Junichiro Koizumi's administration has been delayed until at least Monday, officials said.

The bills are an integral part of Koizumi's sweeping reform agenda, but they are bitterly opposed by many within his own party, who view the state-run postal system as a solid vote-gathering machine, as well as by opposition forces.

Liberal Democratic Party executives had initially sought to hold a final vote at a House of Councilors plenary session Friday, after putting the bills through a special committee of the Upper House on Thursday.