Vast oil and gas deposits are believed to be buried under the Arctic, where climate change is melting sea ice and uncovering new commercial opportunities.
Citgo represents around 5 percent of U.S. crude-oil refining capacity, and cash-strapped Venezuela is reportedly looking to hand it to Moscow.
Igor Sechin's comments follow similar claims from Putin himself.
At least 15 other countries are prepared to back the freeze, says Russia's energy minister.
The Russian government insists state company bosses will still submit their tax returns.