Iran and Russia have made progress towards an oil-for-goods deal sources said would be worth up to $20 billion, which would enable Tehran to boost vital energy exports in defiance of Western sanctions, people familiar with the negotiations told Reuters.
In January Reuters reported Moscow and Tehran were discussing a barter deal that would see Moscow buy up to 500,000 barrels a day of Iranian oil in exchange for Russian equipment and goods.
The White House has said such a deal would raise "serious concerns" and would be inconsistent with the nuclear talks between world powers and Iran.
"The deal would ease further pressure on Iran's battered energy sector and at least partially restore Iran's access to oil customers with Russian help," said Mark Dubowitz of Foundation for Defense of Democracies, a U.S. think-tank.
"If Washington can't stop this deal, it could serve as a signal to other countries that the United States won't risk major diplomatic disputes at the expense of the sanctions regime," he added.