UPDATE 1-Rio Tinto sells 56 pct stake in Alcan cable unit

* Sells stake to private equity firm for undisclosed amount

* Divestment part of asset disposal programme

LONDON, Sept 14 - Rio Tinto, the world's second-largest miner, is to sell a 56 percent stake in the cable division of its Alcan Engineered Products unit to U.S. investment firm Platinum Equity for an undisclosed sum.

The miner has been selling assets to boost a balance sheet damaged by the takeover of Alcan two years ago at the peak of the commodities boom.

Alcan's cable division makes aluminium energy cable products at seven sites in the United States, Canada and China.

Rio Tinto agreed to sell most of its remaining Alcan packaging businesses to Australia's Amcor last month for $2 billion, taking it more than halfway toward its target of selling $15 billion of assets in two years.

Rio's shares were 0.5 percent lower at 2,605 pence at 1525 GMT in London on Monday, underperforming a 0.1 percent stronger index of leading shares.