(Reuters) - BlackRock ( BLK ) committed not to support a delisting of Spanish utility Naturgy for at least three years to win government approval for its acquisition of a stake in the group, a stock market filing by the U.S. fund manager showed.

In the filing BlackRock ( BLK ) also committed to support Naturgy's investment plans and presence in Spain - including its headquarters - and a "prudent dividend policy".

BlackRock ( BLK ) took over the 20.64% stake in Naturgy when it agreed earlier this year to buy infrastructure fund Global Infrastructure Partners, Naturgy's third largest shareholder, in a $12.5 billion deal.

In the filing, BlackRock ( BLK ) said it was forced to take those commitments by the Spanish government, which has the right to block or put conditions on the acquisition of large stakes in listed Spanish companies.

The government approved the deal in September.