This month’s impending merger vote by Dewey Ballantine and Orrick Herrington & Sutcliffe has been postponed as the two US giants push to tie up what would be one of the US’ largest-ever legal unions.

Spokesmen at the two firms cited administrative difficulties for the delay, which has scuppered plans to integrate from 1 January as Dewey Orrick at the start of the combined firm’s proposed financial year. The vote is now scheduled for the middle of January. However, decisions on the make-up of the new firm’s management are at an advanced stage.