Iran's oil minister has indicated that Tehran will boost energy relations with friendly nations, such as China and Russia, amid economic sanctions against the Middle Eastern country.

Javad Owji held an interview with NHK in Tokyo on Sunday. He is in Japan to attend the state funeral of former Japanese Prime Minister Abe Shinzo.

Negotiations between Iran and the United States for salvaging a 2015 nuclear agreement remain stalled, with no prospect in sight for lifting the sanctions.

Owji said Iran is working to attract investment from overseas without waiting for the deal to be restored.

He called on Japanese companies to consider expanding into the Iranian market, stressing that his country is 100 percent ready to accept their investment.

Owji revealed that Iran can produce 4 million barrels of crude oil per day. That's reportedly above levels the country had boasted before the sanctions were imposed.

The minister argued that Iran has been able to increase its crude exports to several countries. They are believed to include China.

Owji added that Iran signed a memorandum of understanding with Russia's state energy giant Gazprom in July for cooperation in the oil and gas industry.

The 2015 agreement was struck between Iran and world powers, including the US, to curb Tehran's nuclear activities in return for relief from sanctions.

But in 2018, then-US President Donald Trump pulled his country out of the accord and re-imposed sanctions.