VIENNA — Oil, gas, banks and more, worth tens of billions of dollars to the highest bidder. Less than 10 days after signing its nuclear deal, Iran formally threw open its doors Thursday to European Union companies, eager to do business – and dozens of firms answered the call.

Amir Hossein Zamania, an Iranian deputy oil minister, told the “Iran-EU Conference, Trade and Investment” forum that by 2020, his country hoped for foreign partnerships for oil and gas projects that alone were worth $185 billion (nearly 170 billion euros.)

But even more than oil and gas are at stake, with Iranian officials also pitching the mining sector, Iran’s automotive industry, and the financial sector, at what they bill as the first forum of its kind since Tehran and six world powers sealed the deal.

Nearly three times the size of France, Iran holds plenty of economic promise. The country of 80 million people generates a $400-billion economy, boasts the world’s fourth-largest oil reserves, the second-biggest stores of natural gas, and has well-established manufacturing and agricultural industries.

Sanctions slapped on Iran are scheduled to be lifted over the coming months as the deal unfolds. But even post-nuclear agreement, Tehran will remain under Western scrutiny for its role in fomenting Mideast unrest and its human rights record.

That appeared to temper the wish for public exposure Thursday. Several people turned down requests for interviews as a few demonstrations outside the Austrian Chamber of Commerce urged participants to shy away from business as usual.

But some said they had no problems with publicly pushing for an end to Iran’s economic isolation.

“This meeting is a confirmation of my point of view that the opening to Iran will gain traction,” said Alexander Schwartz of an Austrian consulting company focused on the water and energy sectors.

Zamania, the deputy oil minister, said the conference was meant as a chance for “networking and to find common ground on how to start new partnerships in Iran.”