Shareholders in commodities giant Glencore and mining group Xstrata are to vote on a proposed $US33 billion ($A32 billion) mega merger at two extraordinary general meetings near Zurich.
Glencore shareholders are first up at 4pm (Perth time) at the company's headquarters in Zug, while Xstrata's vote is planned for 9.15pm (Perth time) in the same Swiss canton.
Both Swiss-based companies had been set to approve the blockbuster merger in September but the deal ran into major resistance from key Xstrata shareholders demanding better conditions.
But for market-watchers, the deal seems assured after Qatar's sovereign wealth fund - which has a 12 per cent stake in Xstrata - said last week that it would now approve Glencore's bid to merge with Xstrata.
The Qatari fund had been holding out for 3.25 Glencore shares for one Xstrata share, but said it would accept the 3.05 final offer.
But in last Thursday's statement the fund said it would abstain from voting on the pay package for the new entity's management group, a major source of dispute in the deal.
As part of the tie-up to create a raw materials juggernaut with sales of $US209.4 billion and operating profit of $US16.2 billion, Xstrata executives are to be paid a total of 179 million euros ($A222 million).
Among the many shareholders critical of the sweetener for Xstrata managers, Standard Life Investments slammed that proposal as "unnecessary" and the result of a "rather rapacious management team and a weak board, and we will be voting against it".
If it gets the go-ahead, the merger will then need the approval of EU regulators who have until November 22 to examine the case.
Analysts say regulators could ask Glencore to shed some of its equity stake in Belgian group Nyastar, the world's leading producer of zinc.