Russia’s Gazprom the world’s top gas producer, has announced that it will take on big new energy projects in Iran, a move likely to anger the United States which wants Tehran isolated over its nuclear work.

State-controlled Gazprom, which supplies a quarter of Europe’s gas needs, said it had agreed to develop more phases of Iran’s giant South Pars gas field and drill in the country’s oilfields. Tehran said the deals had been “almost finalised.”

The deal could raise eyebrows of some investors in Gazprom, one of the world’s top 10 most valued stocks, as it seeks to boost its presence in the United States, which has urged foreign firms to cut business ties with Iran.

The agreement takes place as Iran is calling on Russia to set up an OPEC-style gas group, an idea that has sent jitters among top customers and politicians in Europe.