* Korea Exchange to decide on the request by June 20
* Hyundai Heavy top shareholder with 91.1 pct stake (Adds details)
SEOUL, April 13 (Reuters) - South Korean refiner Hyundai Oilbank filed for an initial public offering on Friday, the Korea Exchange said, defying market concerns that it may delay the float, worth up to $2 billion, partly due to worries over its links to Iran.
Hyundai Oilbank, a heavy user of Iranian crude, initially aimed to list in South Korea as early as May but is now more likely to go public in the second half of this year, as the stock exchange will decide on the request by June 20.
Hyundai Heavy Industries is the biggest shareholder of the company with a 91.1 percent stake and Woori Investment & Securities is the lead manager for the deal.
The planned share sale, which would become the country's biggest IPO this year, comes after the postponement of a $500 million Hong Kong float last month by a unit of China's state-owned aluminium producer due to the impact of Western sanctions on Iran.
Hyundai Oilbank made about 20 percent of its crude purchases from Iran last year, according to industry sources, a higher ratio than that of bigger local peer SK Energy.
Hyundai Oilbank reported a 360.7 billion won ($316.2 million) in net profit last year on 19 trillion won of sales.
($1 = 1140.6500 Korean won) (Reporting by Miyoung Kim; Editing by Himani Sarkar)