"Just as fears of nuclear terrorism are rising, U.S. President Barack Obama's drive to lock down vulnerable atomic materials worldwide seems to have lost momentum and could slow further.

With less than 10 months left in office to follow through on one of his signature foreign policy initiatives, Obama will convene leaders from more than 50 countries in Washington this week for his fourth and final Nuclear Security Summit, a high-level diplomatic process that started and will end on his watch.

A boycott by Russian President Vladimir Putin, apparently unwilling to join in a U.S.-dominated gathering at a time of increased tensions between Washington and Moscow, adds to doubts that the meeting will yield major results."

Matt Spetalnick and David Brunnstrom report for Reuters March 31, 2016. [2]