* Tap worth minimum of $500 mln - leads
* Price guidance 3.2 pct area on 2021s, 4-4.125 pct on 2026s
* Order book worth around $1.75 bln (Adds pricing, size update)
HONG KONG/DUBAI, Oct 12 (Reuters) - Abu Dhabi National Energy Company (TAQA) plans to tap on Wednesday the bond issue it completed in June to raise additional funds worth upwards of $500 million, according to a document from arranging banks.
The firm raised $1 billion in June, split equally between portions maturing in 2021 and 2026.
Pricing guidance for the new transaction has been narrowed to a yield in the area of 3.2 percent on the June 2021s and a range of 4-4.125 percent on the June 2026s, the document said.
The initial thinking on pricing had been in the area of 3.35 percent and 4.125 percent respectively, according to an earlier message from arranging banks.
The order book was worth around $1.75 billion, with interest from investors "slightly skewed" towards the tap of the 2026s, the document added.
A tap offers new bonds with the same documentation as an existing deal.
A TAQA executive said in August it planned to return to the bond market either this year or early in 2017 to manage maturing debts.
Wednesday's transaction is being arranged by Citigroup, Mizuho, Mitsubishi UFJ Financial Group and Standard Chartered. (Reporting by Umesh Desai in Hong Kong and David French in Dubai; Editing by Richard Pullin/Ruth Pitchford)