Canada's Teck Resources on Monday reinforced its rejection of an unsolicited $22.5-billion bid from Glencore, saying the implied value was "an illusion" and telling shareholders its restructuring plan was the only viable option.

Glencore's offer, made public on April 3, includes a plan to simultaneously spin off the companies' thermal and steelmaking coal businesses and rebrand the remaining company as GlenTeck.

Teck CEO Jonathan Price told shareholders that more value could be unlocked through a proposed restructuring in which the Vancouver-based miner would spin off its steelmaking coal unit to focus on copper and other industrial metals.

A shareholder vote on Teck's plan is scheduled for April 26. If it passes, the separation process will then take 7 to 8 weeks to complete.

"A vote against the separation is a vote to maintain the status quo at Teck, and there is no path that includes Glencore acquiring Teck," Price said.

"The modest implied premium in the Glencore-rejected proposal is an illusion," he added. "Scale and diversification do not create value if the quality of the business is contaminated."

Teck said its board has rejected the offer as Glencore did not present a coherent plan for its proposed coal company.

Analysts had last week seen room for an higher offer from Glencore to sway Teck shareholders in its favour.

Glencore boss Gary Nagle called it a "very compelling all-share offer," representing a 20% premium to Teck's closing stock price on March 26, when the bid was made privately.

"This is not just about price," Price said on Monday. "We also see serious structural flaws in the proposal that Glencore has put forward, and we believe that (it) would destroy value for Teck shareholders, and that it has significant execution risks."

The structural flaws would include having an oil marketing business within the base metals vehicle and exposing its shareholders to a big thermal coal business, Teck said last week.

Price said that there are significant opportunities to create synergies between Glencore and Teck without the need for an acquisition or corporate transaction.

In its merger bid, Glencore said there were operational synergies that would improve efficiency and reduce costs between some copper assets, including Teck's Quebrada Blanca Phase 2 (QB2) and Glencore's partly owned Collahuasi mine in Chile.

"The QB2/Collahuasi situation is one example where there could be sharing of infrastructure or optimisation on future expansions...the engagement so far with Glencore has been somewhat disappointing on their side," Price told Reuters on Monday.

Price also said Teck sees synergies and improvements to be made between Glencore's McArthur River zinc operation in Australia and Teck's Trail smelter and refinery in British Columbia.