The IEA, whose scientists are politically neutral and widely respected, has previously declined to give explicit backing for nuclear energy.
But environmental concerns and, crucially, growing fears about the reliability of Russia as a gas exporter, appear to have pushed the IEA towards the nuclear option.
Fatih Birol, the agency's chief economist, told a German newspaper yesterday that nuclear power is "a key part of the solution" to energy policy dilemmas.
Russia has unnerved Western leaders in recent months by hinting that it could disrupt supplies from its vast gas reserves in future.
Such statements "are a warning sign and should open the eyes of European politicians," Mr Birol said.
The IEA is set to publish a wide-ranging study of the global energy market this autumn.
By that time, a British government review of energy generation will have reported. Whitehall officials and MPs alike believe that Tony Blair, the Prime Minister, will take the review as an opportunity to back the building of new UK reactors.
Green groups want the Prime Minister to rule out new nuclear plants in favour of renewable energy sources of power such as wind, wave and solar based technologies.
However, Mr Blair has been openly sceptical about whether renewable sources will be able to provide enough power to fill the gap that is expected when the current generation of ageing reactors is finally decommissioned.
Mr Blair, like Mr Birol, has repeatedly raised the security of imported energy sources like Russian gas as a key consideration when drawing up future energy policy.
Downing Street yesterday continued to fuel speculation about Mr Blair's pro-nuclear sympathies.
"The Prime Minister has been quite open in setting out all the arguments why we need a mix of energy sources, " said a spokesman when asked about the IEA's move.
Any new nuclear power plants would almost certainly be built on the sites of existing reactors, several of which are in Scotland.
The nuclear issue is putting pressure on Scotland's Labour-Liberal Democrat coalition.
Under pressure from the Lib Dems, the Executive has ruled out any new nuclear plants in Scotland until the question of how to dispose of nuclear waste is resolved.
A government report on nuclear waste is due this summer at about the same time as the energy review. Labour sources in London believe that Jack McConnell, the First Minister, would ultimately fall in line with Mr Blair should the Prime Minister choose to back new nuclear plants.
The government's energy review has taken evidence from industry, environmentalists and independent experts.
One of those submissions, from a former government nuclear scientist, was published yesterday and raised fears over the security of nuclear plants.
Dr Frank Barnaby, now a researcher at the Oxford Research Group, a think-tank, warned ministers that a successful terrorist plot to crash a hijacked airliner into one could lead to hundreds of thousands of cancer deaths across the British Isles.