TOKYO (Reuters) - President Barack Obama is set to visit Hiroshima after a Group of Seven summit next month, the Nikkei newspaper said, in what would be the first visit by an incumbent US president to the Japanese city devastated by a US nuclear attack 71 years ago.

Citing an unidentified senior US government official, the business daily on Friday (April 22) said Washington planned to propose to Tokyo a visit by the president on May 27, when the summit wraps up.

In Washington, a White House official said no decision has been made.

Japanese Chief Cabinet Secretary Yoshihide Suga denied the visit was being arranged and declined further comment. Diplomatic protocol means any announcement should come from the US side.

"It is not true that a visit to Hiroshima by President Obama is being arranged between the United States and Japan," Suga told a regular news conference. "The schedule of the US president is a matter for the United States to decide. The (Japanese) government will refrain from comment."

A US warplane dropped the atomic bomb on Hiroshima on Aug 6, 1945, killing thousands of people instantly and about 140,000 by the end of that year. Nagasaki was bombed on Aug 9, 1945, and Japan surrendered six days later.

A presidential visit would be controversial in the United States if it were seen as an apology.

A majority of Americans view the bombings as justified to end the war and save US lives. The vast majority of Japanese think the bombings were unjustified.

US Secretary of State John Kerry said during a visit to the city this month that Obama wanted to travel there, though he did not know if the president's schedule when he visited Japan for the May 26-27 summit would allow him to.

Hiroshima bombing survivors, and other residents, have said they hope for progress in ridding the world of nuclear weapons, rather than an apology, if Obama makes the historic visit.

Hopes for Obama's visit to Hiroshima were raised after a speech in April 2009 in Prague when he called for a world without nuclear weapons. He later said he would be honoured to visit the two cities that suffered nuclear attack.

Kerry, who toured the Hiroshima Peace Memorial and Museum, called its haunting displays "gut-wrenching" and said everyone should visit.

The displays include photographs of badly burned victims, the tattered and stained clothes they wore and statues depicting them with flesh melting from their limbs.