UPDATE 1-India's Tata Steel completes convertible debt swap

* $493 mln securities swapped after $546.9 mln bonds issued

* Convertible securities remaining after swap at $382 mln

* Had hoped to exchange at least $400 mln of securities (Adds details, background)

MUMBAI, Nov 20 (Reuters) - India's Tata Steel (TISC.BO: Quote, Profile, Research), the world's No. 8 steelmaker, said it issued $546.9 million in new convertible bonds in exchange for $493 million of securities as part of a plan to reduce costs and ease repayment obligations.

The amount of convertible alternative reference securities remaining after the swap is expected to be $382 million, Tata Steel said in a statement.

Earlier in November, sources familiar with the matter had told Reuters that Tata Steel expected conversion of at least $400 million worth of securities.

The new foreign currency convertible bonds will have a yield-to-maturity of 4.5 percent and will mature in November 2014, compared with a 2012 due date for the existing convertible alternative reference securities that had a yield-to-maturity of 5.15 percent.

At 0530 GMT, shares in the company, valued at about $10 billion, were down 1 percent at 532 rupees in a Mumbai market .BSESN that had slipped 0.3 percent.

The new bonds are convertible into shares at 605.53 rupees each, 15 percent more than the firm's share price when the offer was made, at a fixed 46.36 rupees to the dollar exchange rate.