JOHANNESBURG (Reuters) -The board of South Africa’s Gold Fields will not change the terms of its offer for Yamana Gold after a surprise rival bid from Agnico Eagle and Pan American, it said on Monday.

Gold Fields’ decision reflects “commitment to capital discipline” and the “fairness” of its offer for shareholders in both Gold Fields and Yamana, the South Africa-listed miner said on Monday.

The joint cash and stock offer from Agnico Eagle and Pan American on Friday trumps the Gold Fields bid, which valued Yamana at a little more than $4 billion at Thursday’s close.

“Gold Fields believes in the highly complementary fit of Yamana’s operating assets,” the company said.

Shares in Gold Fields shares slumped after it announced the all-stock deal in May, denting the deal’s value for Yamana shareholders.

Some investors have criticised the proposed acquisition and Gold Fields shares jumped by 11% on Friday as the market adjusted to the possibility that the deal may be off.

(Reporting by Helen ReidEditing by David Goodman)