U.S. President Barack Obama is considering whether to lift a three-decade-old arms embargo on Vietnam, U.S. officials say, as he weighs calls to forge closer military ties with Hanoi against concerns over its poor human rights record.

The debate within the U.S. administration is coming to a head amid preparations for Obama's trip to Vietnam this month to bolster ties between Washington and Hanoi, former wartime enemies that are increasingly partners against China's growing territorial assertiveness in the South China Sea.

The full removal of the embargo — something Vietnam has long sought — would sweep away one of the last major vestiges of the Vietnam War era and advance the normalization of relations begun 21 years ago. It would also likely anger Beijing, which condemned Obama's partial lifting of the arms ban in 2014 as an interference in the region's balance of power.