South Korea's vice foreign minister has held back-to-back talks with top negotiators of the five countries involved in Vienna-based talks aimed at reviving a 2015 Iranian nuclear deal, its foreign ministry said Thursday.

Choi Jong-kun was in the Austrian capital for the talks as Seoul hopes the restoration of the Joint Comprehensive Plan of Action (JCPOA) would help address the thorny issue of Iranian assets frozen in South Korea under US sanctions.

This week, Choi met with the US Special Envoy for Iran Robert Malley and Deputy Secretary-General of the European External Action Service (EEAS) Enrique Mora, who serves as the coordinator of the Vienna talks, as well as the representatives of France, Germany and Britain.

At the meetings, Choi shared the view that the current round of negotiations has reached "a critical juncture" and called for efforts to achieve "positive progress," the ministry said in a press release.

"Choi reaffirmed that our government will continue diplomatic efforts for progress in Iranian nuclear negotiations and at the same time actively play any role that it can possibly play," the ministry said.

South Korea is not party to the Vienna talks but has keenly watched related developments amid prolonged tensions with Iran over its assets here frozen under US sanctions that were restored after Washington withdrew from the JCPOA under former President Donald Trump in 2018.

His visit came as the ongoing nuclear talks are known to be focusing on the possible relief of US sanctions, which have left about $7 billion worth of Iranian assets frozen in South Korean banks. (Yonhap)