The likely return of Iranian oil is setting up what promises to be an aggressive battle to supply a corner of the coveted Asian market.

Iran is a major producer of condensates—ultra-light oil that’s a by-product from natural gas fields—and South Korea is Asia’s biggest operator of splitters designed to turn it into petrochemicals used to make plastics.

SK Innovation Co., Hanwha Total Petrochemical Co. and Hyundai Oilbank Co. used to favor Iran’s South Pars condensate due to plentiful supply and relatively low prices, but U.S. sanctions saw those flows dry up from 2019. The South Korean refiners then turned to condensates from Qatar and Australia, as well as West Texas Light crude and full-range naphtha from Europe and Africa.

With the Iranian nuclear accord possibly being revived by August, the Persian Gulf nation will be keen to win back its former customers. And while the battle for market share will be centered on Korean condensate buyers, it will also ripple through Asian markets for light crudes and naphtha.

“The fight in the condensate market will be fierce,” said Armaan Ashraf, an analyst at industry consultant FGE in Singapore. “Iran will need to offer South Pars at discounts to incentivize buyers” and that will displace a substantial amount of arbitrage condensate and naphtha across Asia and cause prices to dip relative to benchmarks, he said.

The potential lifting of sanctions on Iranian oil will hit condensate markets much harder than crude due to the relative importance of supplies from the Persian Gulf nation. More than 100 million barrels of South Pars are being held onshore in Iran, or overseas in floating and bonded storage, FGE estimates.

Exports of South Pars during the inventory de-stocking phase, which could last more than a year, could account for more than a third of the East-of-Suez market for traded condensates, the industry consultant said. Once this phase is over, Iran will likely ship around 300,000 barrels a day of South Pars, it said.

Negotiations on the nuclear accord are still facing hurdles, with talks in Vienna adjourned until next week. Both Washington and Tehran will need to make “hard decisions” that could ruffle domestic political constituencies, Enrique Mora, the European Union’s deputy foreign policy chief, said on Wednesday.

Russia’s Deputy Prime Minister Alexander Novak sees some Iranian oil in the market this summer should a deal be agreed, although it depends on factors such as Iran’s “technical capabilities” and its readiness to increase output.

Apart from South Korea, the United Arab Emirates, China, Japan and were among the top buyers of South Pars prior to the sanctions. The grade used to be sold at about $2 a barrel or more below Qatari Deodorized Field Condensate, according to traders, making it one of the cheapest feedstocks.

The world’s biggest condensate splitter capacity is in South Korea, the Middle East and the U.S., meaning these buyers held off making purchases from Iran while the penalties were in place. China—which kept buying limited amounts of Iranian crude despite the sanctions—is not a major market for condensate.