A senior Russian official said Monday that Moscow has started supplying goods to Iran in exchange for crude oil under a 5-year barter deal.

According to Reuters, the US$20 billion deal was being discussed more than a year ago and would involve Russia providing grain, equipment and construction materials in exchange for up to 500,000 barrels per day of Iranian oil.

Also Monday, Russian President Vladimir Putin’s  government lifted its ban on delivery of sophisticated air defense missiles to Iran. The moves come amid the ongoing process regarding Iran’s nuclear program, including a tentative deal between the U.S., Iran and five other world powers reached in Switzerland in early April.

In 2010, Iran's refusal to halt uranium enrichment led the U.N. to impose sanctions against Tehran, which included the ban of the sale of all types of heavy weaponry.

Under then President Dmitry Medvedev, Russia self-imposed the arms ban, generating losses of up to US$13 billion in arms sales to Iran. However, the new resumption of arms exports is expected to compensate Iran while also strengthening the relations between the two countries, both of whom have been hit by U.S.-EU sanctions.

The announcement was welcomed by Iran, however the U.S. and Israeli governments criticized the decision taken by the Kremlin.

According to government sources, U.S. Secretary of State John Kerry objected to Russia's decision in a phone call to Foreign Minister Sergey Lavrov, while the White House said the move could endanger plans to ultimately lift sanctions on Iran.