In an open letter on Wednesday, Glencore said it would consider taking the offer to Teck’s shareholders directly if the board failed to engage.

The Swiss miner and trader made its all-share offer as Teck’s own plan to spin off its metallurgical coal business and focus on copper and zinc nears an April 26 vote.

The bid is the latest in a wave of mining industry buyout offers fuelled by growing demand for copper and other metals critical to the green energy transition.

Glencore Chief Executive Gary Nagle flew to Canada to meet shareholders last Thursday after revising its unsolicited bid to include up to $8.2 billion in cash.

Teck’s board rejected that as too low, adding that it would unnecessarily expose shareholders to a large thermal coal business and an unwanted oil trading unit.

“Glencore has never stated that its proposal is ‘best and final’ and that it is not willing to make changes and improvement to its proposal,” it said in a statement.

“With engagement, we could improve our proposal’s terms and value, which would be in the best interests of all Teck shareholders.”

Glencore’s proposal would combine and spin off its thermal coal unit and Teck’s steelmaking coal business.

Teck’s management on Tuesday estimated that after its proposed restructuring, shares in the metals business could trade at C$100 ($74.67) or higher, about 55% above the group’s closing price on Tuesday.

Glencore’s initial bid, made privately, represented a 20% premium to Teck’s March 26 closing price.

JP Morgan analysts this week said that Glencore could pay as much as $27.2 billion.

Teck has said it would explore a corporate transaction or partnership after its restructuring. Sources close to the matter said Teck has had approaches from more than six mining companies interested in its prized metals business.