News: SXY UPDATE 1-South Korea's POSCO International in talks to buy Australia's Senex Energy

(Adds details on bidding timeline)

Oct 18 (Reuters) - South Korean trader POSCO International Corp 047050.KS made an A$814.8 million ($605.56 million) takeover bid for Senex Energy Ltd (SXY) in September, the Australian natural gas producer said on Monday.

Senex said it was giving POSCO exclusive due diligence access until Nov. 5 to better its already twice-improved bid of A$4.40 per share, with the South Korean firm indicating it would likely push the deal through an off-market takeover if it goes ahead.

POSCO International, the trading arm of South Korean steel giant POSCO 005490.KS , could not be immediately reached for comment.

Senex said POSCO International initially made its approach on July 30 with an A$4-per-share bid, followed up around a month later by an A$4.20-a-share bid.

After the latest bid on Sept. 2, Senex granted POSCO exclusive access to its books, it said.

The latest bid is a 15.2% premium to Senex's close on Friday and a near 38% premium to its close on Sept.1. ($1 = 1.3455 Australian dollars)