BHP confirmed the new offer, which it described as “final,” but said that it would be willing to increase or otherwise improve the share ratio if Anglo’s board agreed to recommend a higher bid or if Anglo received an offer from someone else. BHP struck a more optimistic tone than Anglo, suggesting it sees a path to a deal.

Read More: BHP’s $39 Billion Bid for Anglo American Was Years in the Making

“We have been engaging with Anglo American and its advisors to help mitigate the concerns,” BHP said. “We have made progress on these topics over the course of the engagement so far, and we are hopeful that resolution will be reached in the next seven days.”

The announcement extends a month of drama that has captivated the mining world, confirming the return to mega M&A by the industry’s biggest players after years on the sidelines, while triggering speculation that BHP’s rivals could enter the fray with competing bids. Anglo had already twice rebuffed BHP proposals to first break up and then acquire the company, and instead rushed out a radical restructuring plan of its own.

The news also comes just hours before a regulatory cut-off for BHP to either commit to an offer or walk away for six months under UK takeover rules. Anglo has also agreed to an extension of the deadline to May 29.

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Anglo swung on the news before trading 0.7% lower at £26.68 at 3:41 p.m. London time. They remain 12% below the value of BHP’s bid, which valued Anglo at £30.38 based on Tuesday’s share prices.

“The conclusion here appears to be clear – this new proposal was rejected by Anglo on grounds of structure rather than price,” advisory firm MKP Advisors wrote in a note.

The thrust of negotiations are now likely to focus on Anglo’s South African businesses, which appear to have crystallized as the key point of dispute. BHP has refused to budge. The world’s biggest miner is insisting Anglo first exit its investments in Johannesburg-listed Anglo American Platinum Ltd. and Kumba Iron Ore Ltd., while Anglo repeated its continued objections to the multi-step proposal.

“It does not address the board’s concerns about the structure, which results in significant complexity, execution risks, an extended timeline to completion and consequently has the potential for material value leakage to be disproportionately suffered by Anglo American’s shareholders,” Anglo Chairman Stuart Chambers said.

If the two sides were to reach a deal, it would probably face close antitrust scrutiny and require several layers of approvals in South Africa, where mining is an important employer and Anglo itself has a long history.

Read More: Anglo’s Second-Largest Investor Says BHP Needs to Revise Bid (1)

Earlier on Wednesday, South Africa’s state-owned Public Investment Corp., which is Anglo American’s second-largest shareholder, issued a statement that BHP’s previous offer would require “meaningful revision.” Crucially, the PIC also said that BHP should consider the material risks it was asking Anglo shareholders to take.

The tug-of-war over Anglo’s future is also taking place against the backdrop of surging copper prices, driven by a wave of speculative money betting on future shortages that sent London Metal Exchange futures to a record earlier this week.

While Anglo’s copper assets have long been coveted by rivals, its complicated corporate structure and unusual mix of commodities has largely deterred potential suitors until now.

However, the miner has faced a series of major setbacks over the past year as prices for some of its key products plunged, while operational difficulties have forced the company to slash its production targets — driving down its valuation and leaving the company vulnerable to BHP’s approach.

Anglo Chief Executive Officer Duncan Wanblad last week unveiled a dramatic plan to reshape its business by exiting platinum, diamonds and coal and slowing an unpopular fertilizer project, framing the plan as a better alternative to the deal being proposed by BHP.