The commodities giant had previously stuck to the 2.8 share ratio, but increased it this morning to win support for the merger from Xstrata shareholders. It also wants Ivan Glasenberg to lead the new firm, rather than Xstrata boss Mick Davis as previously agreed.
The increased share ratio now values the merger at $37bn (£23.2bn).
Xstrata and Glencore shareholder Standard Life Investments was supportive of the deal. David Cumming, head of equities at the asset manager, welcomed the new deal as well as proposed changes to governance.
He added: "The deal will, we believe, enhance the growth prospects of the combined group and consequently, as shareholders both of Xstrata and Glencore, we are pleased with the proposed outcome."
But this afternoon, the independent directors of Xstrata issued a statement to Glencore with concerns over the 3.05 share ratio and the premium.
It also questioned putting Glasenberg in charge, adding that scrapping retention plans for Xstrata staff represented "significant risk". "It represents a fundamental change to the governance structure which underpinned the agreed merger of equals," said Xstrata.
The merger meeting, in Zug, Switzerland, between commodity giants Glencore and Xstrata was meant to take place this morning, but was adjourned due to developments overnight.
The mega-merger has been under continued strain over recent weeks.
The increased share ratio comes after Xstrata shareholder Qatar Holding, which owns 12 per cent of the firm, rebuked the 2.8 ratio and said it would snub the deal if Glencore didn’t come forward with better terms.
It wants 3.25 new Glencore shares for each Xstrata share for shareholders.
Glencore this morning requested its shares be suspended on the London and Hong Kong stock exchanges, although they were still trading following the announcement. Glencore closed down 3.92 per cent down today at 376.95p.
Charles Gibson, head of mining for Edison Investment Research, said: "Should the deal go ahead via a higher offer, it would be a vindication of Xstrata shareholder concern about long term fundamentals being fairly valued, while for Glencore the pressure will be on to prove that the higher price was justified.
"In the meantime, it remains to be seen whether Xstrata shareholders will have the patience to back some of the Xstrata board at a new enlarged Glenstrata."
In a research note yesterday, broker Liberum Capital gave the deal only a 30 per cent chance of going through.