Iran and South Korea have started working-level consultations on ways to resolve yearslong disputes over Tehran's assets frozen in Seoul under US sanctions.

The South Korean foreign ministry said on Wednesday that Iranian bankers and officials from the state-run oil company and the petroleum ministry have traveled to Seoul to meet with South Korean government and company officials.

During the two-day meetings that started on Tuesday, the two sides discussed detailed payment options and the possibility of resuming oil trade if the US grants sanctions relief.

As the Vienna talks to revive the 2015 nuclear deal seem to be in the final stages, Iran appears to be taking steps for its official return to the international oil market after more than three years.

According to Citigroup, a possible agreement would allow the return of 500,000 barrels a day of oil to international markets in April to May, eventually rising to 1.3 million barrels by year-end.

Iran, which sits on the world's fourth-largest oil reserves, had been a key oil supplier to South Korea, and a main importer of goods such as industrial equipment, household appliances and vehicle parts.

Seoul stopped purchase of Iranian oil since in May 2019 due to sanctions that ban the Islamic republic's oil exports.

Two South Korea banks hold $7-9 billion of Iranian money, owed for oil imports, but the funds are locked under US sanctions, which were reimposed after former President Donald Trump in 2018 withdrew from the deal.