Russia built Iran’s sole existing nuclear power plant in the Gulf port of Bushehr and handed it over to Iranian engineers last September.

Iran’s ambassador in Moscow said last month that Russia could build a second nuclear power plant in Bushehr as part of a swap deal for oil that has sparked strong opposition in Washington because of its implications for Western sanctions on Iran’s vital oil sector.

“Nikolai Spassky, Rosatom’s deputy director general for international affairs, will arrive in Tehran on Tuesday to hold talks with Iranian officials about the construction of a new nuclear power plant,” Iranian Atomic Energy Organisation spokesman Behrouz Kamalvandi said.

“Our plan is to build up to four power plants in Bushehr. Of course, we will have to see how the talks progress,” Kamalvandi told the official IRNA news agency on Monday.

Last month, Iran’s ambassador to Russia, Mehdi Sanaei, said the two close trading partners have been negotiating Iran’s delivery of hundreds of thousands of barrels of oil per day (bpd) in return for Russian goods and services.

Russian officials have neither confirmed nor denied the discussions, while stressing that they would not break UN sanctions.

But the White House has raised “serious concern” about the potential of the mooted deal to undermine EU and US sanctions which are estimated to have shrunk Iran’s crude exports from 2.5 million bpd to less than one million since late 2011.

One Russian report said the barter deal could see as much as 500,000 bpd of Iranian crude exchanged for Russian goods, which Sanaei said could also include heavy trucks and railway equipment.

That would represent a boost of more than 50 percent to Iran’s crude exports, undermining crippling sanctions on its oil and banking sectors that Western governments credit with securing its signature to a long-sought nuclear deal last November.

Talks between Iran and the major powers, including Russia, continue on a long-term agreement to allay Western concerns about Iran’s nuclear ambitions.