This update on Xstrata's merger overture to Anglo American is just in. Anglo is one of the partners in Pebble.

LONDON (AP) — Mining company Anglo American roundly rejected a merger proposal from its Anglo-Swiss rival Xstrata Monday, saying it made little strategic sense and that the terms were unacceptable.

Anglo American’s board said a tie-up with its competitor would be a big blunder because the move would dilute the company’s exposure to platinum and diamond markets, while increasing its exposure to nickel and zinc — base-metals whose prices have been hit hard by the global economic slowdown.

“Irrespective of this lack of strategic merit, the terms proposed by Xstrata were completely unacceptable,” the board said in a statement.

Xstrata, which last year failed in a bid to take over another rival, Lonmin, had said that the case for combining the two companies was “highly compelling” and would lead to substantial cost savings.

The merger would have created a group worth $68 billion based on Friday’s closing share prices, ranking the combined company behind BHP Billiton and Rio Tinto.

News of the proposal drove Anglo American shares up 4.6 percent at $27.75, while Xstrata’s stock dropped 6.7 percent on the London Stock Exchange. Anglo's gain was less on U.S. markets later in the day.

Xstrata did not immediately return a call seeking comment late Monday.

Mining companies have been hit by a slump in demand in recent months, leading Xstrata to make last year’s hostile $8.9 billion takeover approach for Lonmin.

After fighting off the bid, Lonmin announced plans to suspend some of its mining operations and reduce its work force to adapt to a drop in demand for platinum caused by a downturn in sales of jewelry and cars.

Anglo owns South Africa’s Anglo Platinum, the world’s largest platinum producer. Xstrata is the world’s largest exporter of coal for power stations.