(ShareCast News) - Rio Tinto has arranged a further $3bn reduction in its gross debts after agreeing further purchases of its bonds in New York.The mining group's has agreed to buy back $1.252 billion of debt under a 'maximum tender offer', which began on 7 June.This comes on top of the $1.748bn agreed for repurchase under its 'any and all' offer.Under the maximum tender offer, Rio has agreed to buy $488m of Rio Tinto Finance (USA) 3.500% notes due in 2020, $338m 4.125% notes due in 2021 and $401m of 3.750% notes due in 2021, plus a small amount of 3.5% notes due in 2022 and 2.875% notes due in 2022.The securities purchased will be retired and cancelled and no longer remain outstanding.