If reports about an energy deal between Iran and Russia are true, it would be a concern to the U.S. government, State Department spokeswoman Jen Psaki said.

Iranian Energy Minister Hamid Chitchian met Sunday in Tehran with Russian Energy Minister Alexander Novak to discuss upgrading Iran's power plants and electrical transmission lines. Both sides already work together in the nuclear sector, with Russia supplying fuel for Iran's Bushehr nuclear facility.

Russia is under pressure from a U.S. government frustrated with the Kremlin's reaction to Ukraine's move toward the European Union, while Iran is facing its own pressure from sanctions imposed for its controversial nuclear program.

Psaki told reporters during her regular press conference Tuesday she had no confirmation the bilateral energy deal was in place.

"If it were true, it would be of concern," she said.

Novak said earlier this week the electricity deal could extend to Azerbaijan, Iran's neighbor to its north.

Psaki's comments followed a decision from the U.S. Treasury Department to sanction Emirati and Pakistani nationals for evading sanctions targeting Iran's oil sector.