Republican presidential nominee Donald Trump on Sunday questioned why United States President Barack Obama did not mention the Japanese attack on Pearl Harbor during his trip this week to Japan.

'Does President Obama ever discuss the sneak attack on Pearl Harbor while he's in Japan? Thousands of American lives lost. #MDW,' tweeted Trump.

According to CNN, Obama did not publicly mention the surprise 1941 attack that pulled the US into World War II while on his historic trip to Japan, during which he became the first sitting US president to visit Hiroshima.

"Why do we come to this place, to Hiroshima? We come to ponder the terrible forces unleashed in the not-so-distant past. We come to mourn the dead ... their souls speak to us and ask us to look inward. To take stock of who we are and what we might become," Obama said during his visit to the city's Peace Memorial Park.

Earlier in the week, in a joint press conference with Obama, Japanese Prime Minister Shinzo Abe said he had no plans to visit Pearl Harbor.