Iranian media reports local companies outnumber the number of foreign entities registered to attend an oil and natural gas conference in May in Tehran.

Tehran is slated to hold a three-day conference starting May 5 to highlight oil and gas opportunities that have emerged since July, when Iran signed off on a comprehensive plan to ease international concerns that it was developing a nuclear weapon.

Sanctions pressure from European mechanisms eased in January and Iran has since hosted delegates from European oil and gas companies looking to return to the oil- and gas-rich post-sanctions market.

The Iranian Students News Agency reports 35 countries are sending representatives to the event in Tehran, though the 995 local firms registered for the event contrast with the 634 foreign companies that have completed their registrations.

Existing U.S. sanctions pressure on Iran makes it difficult to conduct financial transactions with Iran.

An Iranian summit in London in February was postponed indefinitely because Iranian delegates were having difficulty getting visas to attend the event. Event organizer CWC Group Ltd. said that was the third time the London conference was postponed. Before February, delays were in response to the political situation in Iran and uncertainty surrounding sanctions imposed on Iran in response to its controversial nuclear program.

Iran aims to regain a market share lost to sanctions by ramping up production and exports of crude oil. The Organization of Petroleum Exporting Countries, of which Iran is a member, reported Iranian crude oil production in March at 3.3 million barrels per day, about 11 percent higher than in January.

A tanker of crude oil, the first to leave Iran since mid-2012, left for the European market last month. The International Monetary Fund, meanwhile, said the economy is outperforming its oil-rich counterparts in the region.