President Barack Obama has said Venezuela has the right to develop a peaceful nuclear energy programme, but must "act responsibly".
Mr Obama was reacting to news Russia is to build a nuclear power plant there as part of a series of energy deals.
Mr Obama said he hopes to improve US-Venezuela relations and said the US has no interest in increasing tensions.
Meanwhile, Venezuelan President Hugo Chavez met Iranian leaders for talks expected to focus on energy.
"We have no incentive nor interest in increasing friction between Venezuela and the US, but we do think Venezuela needs to act responsibly," Mr Obama said at the White House.
Last week, Russian media reported the country will build two 1,200 megawatt nuclear reactors at a plant in Venezuela.
Also Rosneft, Russia's state oil giant, will buy a 50% stake in German refinery firm Ruhr Oel from Venezuelan state-owned company PDVSA.
The agreement, worth $1.6bn (£1bn), was signed at the Kremlin during Mr Chavez's visit last week. However the cost of the nuclear deal was not immediately revealed, and it was unclear when construction was to be begin.
Mr Chavez has insisted Iran aim only for nuclear power. Despite the Opec member state's vast oil and natural gas reserves, it has suffered severe electricity shortages.