There are early dividends ahead of formal meetings today at a nuclear summit in Washington.
China has agreed to work with the U.S. on possible sanctions against Iran and Ukraine has decided to rid itself of nuclear bomb-making materials.
President Barack Obama is scheduled to deliver remarks at the opening plenary session.
The leaders are discussing a plan to secure all vulnerable nuclear materials worldwide within four years. The goal is to keep those materials out of the hands of terrorists.
Obama's counterterrorism chief warns that al-Qaida is vigorously pursuing material and expertise for a bomb.
The summit ends later today with a joint declaration to guide future work toward locking away and cleansing the globe of materials still too easily accessible to terrorists.