Trader Glencore has raised its offer for miner Xstrata in a dramatic 11th-hour attempt to rescue one of the sector's largest ever deals from collapse after months of opposition from rival shareholder Qatar.

Glencore chief executive Ivan Glasenberg lived up to his reputation as an unpredictable dealmaker, with overnight talks with Qatar that unlocked an impasse between Xstrata's top two investors. Dawn telephone calls yesterday put the now $36 billion deal back on the table, sources familiar with the deal said.

Glencore, which has a 34 per cent stake in Xstrata already, is proposing an offer of 3.05 new shares for every Xstrata share it does not already own, up from 2.8 per cent.

Qatar, Xstrata's second largest shareholder, demanded a ratio of 3.25 in June, though in recent days sources involved in the deal had said the Gulf state's sovereign wealth fund could settle for a compromise.

'Ivan showed what everyone suspected - he needs this deal more than anyone else,' said one source familiar with the deal.

The new proposal released by Xstrata, however, makes other changes, including placing Glasenberg as chief executive of the new group instead of Xstrata's Mick Davis, a veteran manager with a strong operating record who would have taken the helm under the original deal.

The role for Davis and his team, if any, in the future company is unclear under Friday's proposal, and the change could draw an end to the South African manager's career at Xstrata after a decade at the top. Looking tense and tired at Xstrata's shareholder meeting, Davis declined to comment on his plans.

Glencore also said it might change the offer's structure, from a complex arrangement that requires 75pc approval of non-Glencore shareholders, to a straightforward takeover requiring a simple majority of Xstrata shares.

But the proposals, still not a firm offer from Glencore, were far from certain yesterday to pull the deal over the line. Xstrata directors registered their objections and several sources said it was not clear Qatar backed either the management changes or the shift to a simple takeover.

Xstrata cited a letter from its independent directors to Glencore which questioned the revised offer's 22pc premium to Thursday's closing price as 'significantly lower than would be expected in a takeover' and criticised the intention to replace Davis and to change incentives for executives to stay with the company as a 'significant risk' to its operations.

Sources close to the deal said Qatar supported the new share ratio but not necessarily the move to a takeover structure or Davis' removal as chief executive. Qatar, which had not held talks with Glencore for two months before Thursday night, has not yet commented on the offer.

Glencore's bid had been heading for the rocks after Qatar, with 12pc of Xstrata, said it would vote down the deal unless it was improved.-Reuters