Mining giant Rio Tinto intends to undertake a strategic review, including a possible divestment of the Pebble mine prospect in south-west Alaska.

The Pebble Project is located in the Bristol Bay region in south-west Alaska, approximately 200 miles from Anchorage.

Rio holds 19% equity in Pebble mine, which is a green field project based on a copper-gold-molybdenum porphyry deposit, and is considered to be the largest deposit of its kind in the world.

"As part of its review, Rio Tinto will consider the Pebble Project’s fit with the group’s strategy of investing in and operating long life and expandable assets," Rio Tinto said in a statement.

Rio’s decision comes just days after the chief financial officers of California and New York City wrote to the London-based mining company and urged it to pull out of the Pebble project.

"Any association with Pebble Mine could result in substantial adverse public relations and potential customer and investor backlash," the letter stated.

The main controversy over the mine’s development is that the project could endanger salmon and other fisheries in the Bristol Bay region.

The project also has met severe opposition from other mining companies too.

Last September, Anglo-American moved out of the project, leaving an investment of some $540m, and Mitsubishi Corporation sold out in 2011, citing a re-evaluation of its copper assets.

Pebble is one of the largest copper discoveries in the world, although the ore body contains less than 1% copper by volume.

Metallic minerals found at Pebble include pyrite, chalcopyrite, molybdenite and bornite along with certain amounts of covellite, chalcocite, digenite and magnetite.