Shares of Australia's BHP Group fell over 3% on Thursday, a day after smaller rival Anglo American rejected its third takeover proposal and agreed to a one-week extension for the deadline to make a binding offer.
Shares of BHP fell as much as 3.8% to A$44.47 by 00:26 GMT.
BHP, the world's biggest listed mining group, now has until May 29 to make a binding offer for Anglo American or it will be forced to walk away for at least six months, under the UK's takeover rules.
BHP's latest 29.34 pounds per share approach, based on undisturbed share prices at market close on April 23, valued London-listed Anglo at 38.6-billion pounds. The offer was still conditional on Anglo unbundling its platinum and iron-ore assets in South Africa.
The May 29 deadline coincides with general elections in South Africa, where Anglo was formed and is still of significant national importance.
Last week, Anglo announced plans to either spin-off or sell its less profitable coal, nickel, diamond and platinum businesses to refocus on copper.
Anglo's shares closed up 0.4% at 26.98 pounds on the London bourse on Wednesday.