President Barack Obama will travel to Hiroshima this month in the first visit by a sitting US president to the site where the United States dropped an atomic bomb.

The White House said Obama will visit along with Japanese Prime Minister Shinzo Abe during a previously scheduled visit to Japan.

Obama's visit will bolster his call for denuclearization and honor victims of the bombing that killed 140,000 Japanese on Aug 6, 1945.

The president's visit had long been anticipated. Last month, US Secretary of State John Kerry visited the memorial to the Hiroshima bombing.

The White House has ruled out the possibility that Obama will apologize for the bombing of Hiroshima.

During his 10th trip to Asia, Obama will also visit Vietnam.

US officials said Obama is considering whether to lift a three-decade-old arms embargo on Hanoi.

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.

Boosting the security of allies and partners has been a major thrust of Obama's strategic "pivot" toward the Asia-Pacific region, a centerpiece of his foreign policy.

One major factor in Obama's decision will be whether Vietnam will move forward on major US defense deals, a potential boon for US jobs that could soften congressional opposition to lifting the weapons ban, according to one source close to White House policymaking.

There have been questions about whether Hanoi, which has relied mostly on Russian weapons suppliers, is ready to start buying US-made systems. Diplomats have seen increasing signs that Hanoi is seeking ties with US defense contractors but Washington wants tangible commitments, according to the source.