LONDON Buying Teck Resources' coal business as a standalone unit is a "distant second" for Glencore and Teck should not leave out the Swiss miner if it keeps pursuing its separation plan, boss Gary Nagle told the Bank of America conference in Barcelona on Tuesday.

Teck has rebuffed the Swiss miner and trader's $22.5 billon offer to combine the two companies, instead pursuing plans to separate its copper and coal business.

But the Vancouver-based miner in April had to scrap its initial business separation proposal after failing to secure enough shareholder support, going back to the drawing board to rework what it said would be a "simpler and more direct" split.

Glencore's plan would combine and spin off its thermal coal unit and Teck's steelmaking coal business.

"Doing the full deal is the best offer for both sets of shareholders, it creates the most value – buying their coal business standalone is a distant second in terms of potential benefits," Nagle said in a fireside chat at the conference, according to a Bank of America note.

"If that is the route they go down I think it would be remiss of Teck in terms of value for shareholders to not include us in that process," Nagle said.

As part of its proposal, Glencore has offered up to $8.2 billion in cash to Teck shareholders who may not want exposure to thermal coal, the most polluting fossil fuel.

Speaking separately at the same conference, Teck CEO Jonathan Price repeated that separation "is the path to create the greatest value" for shareholders and said "we haven't heard anything further from Glencore with respect to changes to (their) proposal".

Glencore said it is willing to increase its offer.

(Reporting by Clara Denina, additional reporting by Pratima Desai; editing by Ed Osmond)