Tokyo - US President Barack Obama wants to begin a visit to Japan a day later than planned so he could take part in a memorial service for 13 people killed in a shooting rampage at a US military base, news reports said.

Obama requested that the start of his first visit to Japan be moved back from Thursday to Friday and the Japanese government was expected to grant the request, an official in Japan's Foreign Ministry was quoted as saying.

Japan is to be the first stop in a four-nation Asian trip for Obama, who is to also travel to China and South Korea and attend the Asia-Pacific Economic Cooperation summit in Singapore next weekend.

Before he departed, however, a gunman on Thursday opened fire at Fort Hood in Texas, the largest US military installation in the world, and killed 13 people before being wounded.

The suspect in the attack, Major Nidal Malik Hasan, was an army psychiatrist who was to be deployed to Afghanistan. (dpa)