President Obama, who has weighed ruling out a first use of a nuclear weapon in a conflict, appears likely to abandon the proposal after top national security advisers argued that it could undermine allies and embolden Russia and China, according to several senior administration officials.

Mr. Obama considers a reduction in the role of nuclear weapons as critical to his legacy. But he has been chagrined to hear critics, including some former senior aides, argue that the administration’s second-term nuclear modernization plans, costing up to $1 trillion in coming decades, undermine commitments he made in 2009.

For months, arms control advocates have argued for a series of steps to advance the pledge he made to pursue “a world without nuclear weapons.” An unequivocal no-first-use pledge would have been the boldest of those measures. They contend that as a practical matter no American president would use a nuclear weapon when so many other options are available. Continue reading.