Toronto — Barrick Gold, the world’s second-largest gold miner, believes its proposed offer to take full control of its African unit is “more than fair” and will engage with Acacia Mining’s board and minority shareholders to win them over, CEO Mark Bristow said on Tuesday.

Acacia agreed on Tuesday to extend to July 9 the deadline for Toronto-based Barrick to make a firm offer to acquire the 36.1% of the company it does not already own.

Barrick’s May 21 share-for-share proposal valued Acacia at $787m, a near 9% discount to its pre-offer closing price, drawing protests from Acacia’s minority shareholders. After a 17% gain in Barrick shares driven by a gold price rally, the value had increased to $887.8m by Monday, a 6.8% premium. On Tuesday, Barrick shares closed up 1.3% at C$19.26 ($14.37) in Toronto.

“We’ve looked at the assets, the mine plans, and we felt our offer was more than fair based on our due diligence,” Bristow said in an interview. “There’s still significant operational risk in these assets.”

Acacia shares have risen 12% since the original proposal, and closed broadly in line with the offer value on Tuesday.

Some Acacia minority shareholders remain unconvinced.

“No-one has ever won a takeover by approaching a company, offering a discount … at the same time going against their own internal valuation, and then subsequently producing a bunch of new assumptions that make no logical sense for anyone, except the bidder,” said a top-10 Acacia shareholder, who requested anonymity.

Barrick valued Acacia’s assets at $1.3bn in its 2018 annual report but said on Tuesday it had concluded, based on its review, that certain of Acacia’s assumptions were not supportable.

Barrick has expressed willingness to Acacia’s minority shareholders to discuss the offer and expects to engage with them in the coming weeks, Bristow said.

“I’ve never been one that draws a line in the sand without proper engagement, and we’re committing again to engagement,” Bristow said. “But no-one’s come up with an alternative.”

Barrick’s proposal followed two years of wrangling over a $190bn Tanzanian tax bill, with Acacia shut out of talks with the Tanzanian government and Barrick negotiating on its behalf. A proposed settlement included a $300m payment to the Tanzanian government and a 50-50 split of the mines’ economic benefits.

In the absence of a final deal with Tanzania, Acacia is expecting to go ahead with an international arbitration hearing in July, with an outcome expected by the end of 2019.