U.S. Deputy Energy Secretary Daniel Poneman said after a nuclear energy security working group meeting between the two countries that both nations have developed a "strong partnership" in the field.
Despite disagreements over the Syrian crisis and a rift over U.S.-led missile defense plans for Europe, Moscow and Washington have cooperated on key global issues such as the war in Afghanistan, counter-terrorism and nuclear security.
Under a 2005 agreement, they have both been closely cooperating in returning fuel from Soviet-designed reactors built overseas for reprocessing to reduce the danger of highly enriched uranium falling into the wrong hands.
"We are talking about the situation in which a matter of kilograms of this material is highly dangerous and could be used for terrorist purposes, and which we have repatriated many multiples of that quantity," Poneman told reporters after the talks.
Russia's Rosatom nuclear agency chief Sergei Kiriyenko said it has already removed a total of more than 4,400 pounds (over 2,000 kilograms) of highly enriched uranium from research reactors in six former Soviet republics and Soviet bloc nations.
"We are talking about hundreds of potential 'dirty bombs' that could have fallen into the hands of terrorists," Kiriyenko said. "Russia and the U.S. have taken responsibility for security in all the countries which we have supplied with highly enriched uranium."
Poneman said that the effort envisages the replacement of highly enriched uranium for low enriched, allowing the countries to continue operations for scientific applications.
Poneman and Kiriyenko also signed a statement Tuesday confirming Russia's intention to begin conversion of its own research reactors from highly enriched to low enriched.
They added that U.S. and Russian officials are finalizing the text of a bilateral agreement on research and development in nuclear energy that is expected to be ready for signing in September. The agreement is intended to set the framework for shared efforts in designing prospective nuclear reactors and fuel.
"We continue to believe that the proposed activities will give additional momentum to establishing long-term and large-scale cooperation between Russia and the United States in civil nuclear energy and in nuclear security," Poneman said.