Speaking to reporters on the sidelines of an energy forum in the Russian city of St Petersburg, Novak said oil demand in the third and fourth quarters of this year was still unclear.

He said his ministry was discussing the future of the deal with Russian energy companies.

"It's too early to say," Novak said when asked about an extension of the deal.

"We need to wait for, among other things, the G20 heads of state meeting."

"Let's see what questions they discuss there, how the economy develops, the situation on the market.