Russia and the United States signed on Tuesday a long awaited civilian nuclear cooperation pact that will allow firms from the world's two biggest atomic powers to expand bilateral nuclear trade.
The deal will open up the booming U.S. nuclear market and Russia's vast uranium fields to firms from both countries.
Without a deal, cooperation potentially worth billions of dollars was severely limited and required official consent.
Russia's state nuclear corporation Rosatom said in a statement the deal signed by its head Sergei Kiriyenko and U.S. ambassador to Russia William Burns, would create the legal basis for such cooperation.
"The signing of the document ... will provide for the normal development of atomic energy and the nuclear fuel cycle while reducing the risk of the proliferation of atomic weapons," the Rosatom statement said.
At the 2006 Group of Eight summit in St Petersburg, U.S. President George W. Bush and Russian President Vladimir Putin blessed the deal but it has faced opposition from some U.S. congressmen because of Russia's cooperation with Iran.
On Wednesday, Putin will formally hand over powers to his successor, ally Dmitry Medvedev, who was elected in March.
"It is symbolic that it will be signed on the last day of Vladimir Putin's presidential term," a Russian official told Reuters.
A 123 agreement, so-called because it falls under section 123 of the U.S. Atomic Energy Act, is required before countries can cooperate on nuclear materials.
Some U.S. politicians have said nuclear cooperation with Russia should be shunned because Russia is helping Iran build an atomic power station, but the Bush administration is keen to have the pact approved this year.
Once the agreement is signed Bush will have to send it to Congress, which has 90 days to act. If Congress does nothing, the agreement goes into effect. If lawmakers want to block it, they must pass a resolution of disapproval. Russia's parliament, which is controlled by Putin's party, must also ratify the treaty.
Russia, one of the world's biggest sellers of enrichment services, has been trying to break into the prosperous nuclear markets of the United States and European Union.
Tuesday's agreement simplifies life for companies in both countries allowing them to strike deals on trade in nuclear materials directly among themselves.
"You cannot overestimate the importance of this agreement because it opens up the giant north American market for nuclear materials to Russian companies," said Vladimir Yevseyev, a senior researcher at the Moscow Centre For International Security.
Putin has reformed Russia's nuclear sector to boost competition and open it up to world atomic firms such as Japan's Toshiba Corp, which owns U.S.-based Westinghouse Electric.
Russia has crafted a nuclear behemoth called Atomenergoprom -- which officials say is an atomic version of Russian gas giant Gazprom -- to compete with the biggest nuclear companies on the world market.