Diplomats from EU member states have started to prepare a package of sanctions against Iran with a goal of formally adopting them at a meeting of foreign ministers on 15 October in Luxembourg.
"There is agreement on gas," one of the diplomats said, speaking on condition of anonymity. "The big states back it, Germany, Britain, France," another one said.
The fresh sanctions also consist of various finance and energy-related proposals, three EU diplomats said on Thursday (4 October).
The moves come as European governments and the United States are searching for new ways to pressure Tehran into scaling back its nuclear work after diplomacy foundered earlier this year. Tehran denies its work has any military intentions.
But tensions over the issue are on the rise, with Israel threatening to strike Iranian uranium enrichment installations.
The United States, since 1995, has banned US firms from investing in Iranian oil and gas and from trading with Iran.
The European Union has been much slower to ban Iranian energy. It imposed an embargo on Iranian oil this year, after banning the creation of joint ventures with enterprises in Iran engaged in the oil and natural gas industries in 2010.
Existing sanctions cover investment in Iranian gas, but do not specifically outlaw imports, which are insignificant In terms of volume, but symbolic.
The EU sources said Iranian crude reaches Europe via Turkey, which blends it with Azeri gas and ships it on.
They said there was a risk of the new measure alienating Turkey, which has a pivotal role to play in its plans to diversify gas supplies away from dominant supplier Russia, but it was a risk worth taking.
Turkey controls a huge chunk of a planned new export route for shipping Azeri gas, which would link up with one of two short-listed pipelines to complete the journey into the EU.