Tehran urged Seoul on Sunday to release billions of dollars of Iranian funds frozen in South Korea under US sanctions over its nuclear programme, during a visit by the South Korean premier.
"We call on the Korean government to release Iran's financial resources as soon as possible," Iran's First Vice President, Eshaq Jahangiri, said alongside Prime Minister Chung Sye-kyun in Tehran.
Mr Chung's visit came after Iran on Friday released a South Korean-flagged tanker it had seized three months ago, as Tehran pressed Seoul to unblock billions in frozen oil funds.
Iran accused South Korea of holding "hostage" $7 billion of its funds, but Tehran has repeatedly denied that the seizure of the vessel was linked to the issue.
Mr Jahangiri said South Korea "needs to step up co-operation with related nations including Iran" to settle the issue.
"South Korea's visit to Tehran is an expression of it's commitment to building a forward-looking relationship between the countries," he said.
Iran was a key oil supplier to South Korea until Seoul stopped its purchases after a US decision in 2018, under then-president Donald Trump, to leave the Iran nuclear deal and reimpose sanctions.
New US President Joe Biden has indicated his readiness to revive the accord.
Negotiations are under way in Vienna between Iran and the other state parties to the 2015 deal – Germany, China, France, Britain and Russia – to salvage the accord and lift sanctions on Tehran.
Mr Sye-kyun said his country is willing to support Iran to advance its dialogue with the international community to restore the nuclear deal.
Humanitarian co-operation is expected to increase and a special consultative body to administer economic co-operation will be established if the Iran nuclear deal is restored, the two officials said.
He is expected to meet with Iranian President Hassan Rouhani and Mohammad Bagher Ghalibaf, Iranian parliamentary speaker, on Monday in Tehran as part of his visit to the country.