Iran's Central Bank chief Valiollah Seif said his country took possession of a 13-ton hoard of gold - worth nearly $500 million - held up by sanctions after working out a deal on the sidelines of nuclear talks in Vienna, USA Today daily reported Friday.

"A sum of 13 tons of gold that had been purchased before and was deposited in South Africa in the past two years and could not be transferred to Iran due to the sanctions … was delivered to the Central Bank of Iran's treasury last night," Valiollah Seif, who heads the Central Bank of Iran, said Wednesday, according to the Iranian state-owned Fars News.

Seif said the transfer is evidence the talks are having some success.

The retrieval of the gold was the result of months of hard work. That much gold is worth about $485 million based on current price per ounce.

The State Department said the timing was unrelated to the current talks but rather stems from an interim agreement reached in November 2013.

That deal suspended sanctions on trade with Iran in gold and precious metals starting January 2014.

Iran is negotiating with the five original nuclear members of the United Nations Security Council- the USA, Britain, France, Russia and China- plus Germany on a deal to lift crippling international sanctions in return for limits on Iran's nuclear program.

Negotiators extended a Tuesday deadline for another week and are now seeking a deal by July 7.

The agreement is intended to ensure Iran's nuclear program remains as peaceful as that nation claims it is.