Anglo American on Wednesday rejected a request by BHP to extend takeover talks, a week after it rejected a third £38.6 billion ($49 billion) proposal from the Australian mining giant.

Under the UK Takeover Code, BHP has until 5 pm UK time on 29 May to make a formal bid. This deadline had been previously extended by a week.

While Anglo rejected BHP’s third takeover offer last week, it agreed to continue talks with the Australian miner – a move experts saw as encouraging for the deal to go through.

In a statement early on Wednesday, BHP says it welcomed the opportunity to engage with Anglo regarding its concerns over the proposal, adding it has continued to work to address those concerns.

“BHP believes a further extension of the deadline is required to allow for further engagement on its proposal,” the company notes. “BHP is confident that the measures it has proposed to the board of Anglo American provide a viable pathway to resolve the matters raised by Anglo American and would support South African regulatory approvals.”

All three previous proposals by BHP required Anglo to sell its stakes in Anglo American Platinum and Kumba Iron Ore assets in South Africa to its shareholders. The structure was one of the key reasons for Anglo’s board to reject the offer, saying it would create “material completion risk” and “value impact.”

Calling the associated risks “quantifiable and manageable,” BHP says it has already factored in the costs of the potential risks into its proposal, Kallanish notes.

The Australian miner says it is willing to discuss a “reverse break fee,” if the deal is blocked due to anti-trust reasons or if it fails to secure regulatory approval. It has also included socio-economic initiatives in South Africa in its offer to Anglo, including increased South African employee ownership of the South Africa-listed businesses.

However, Anglo says BHP’s socioeconomic measures are “confined in scope, impact and duration.”

“This approach does not sufficiently address the fact that Anglo American’s shareholders would bear disproportionate execution and value risks and uncertainty over an extended period, nor does it consider that material conditions would likely be imposed in relation to both Anglo American Platinum and Kumba which would require the approvals of their respective boards,” the company states.

Anglo estimates the “complex structure” proposed by BHP would take over 18 months to implement, throughout which there would be “material risks to completion and uncertainty around the value delivered to Anglo American shareholders.” Its board has unanimously concluded that “there is no basis for a further extension to the PUSU [put up or shut up] deadline.”

BHP will now have to make a firm offer by the deadline. Otherwise, it will either have to walk away or wait six months to make another offer.