The future of Anglo-Dutch steelmaker Corus, which employs 8,000 in Wales, will be decided this week in a quick-fire auction.
Brazilian steel group CSN is tipped to trump Indian rival Tata in the £6bn-plus battle.
The long-running contest could be all over by early Wednesday morning after the Takeover Panel announced an unusual set of rules to bring the matter to a head.
There will be nine rounds of bidding, starting at 4.30pm on Tuesday, and lasting 10 hours.
There is an option for the panel to freeze the auction and continue the following evening, but City sources said that they expected the action to be fast and furious, and the steel company's fate to be sealed by Wednesday morning. CSN is widely expected to outgun Tata.