TOKYO - US President Barack Obama will make a surprise early appearance at the APEC summit dinner in Singapore on Saturday, after bringing forward his departure from Japan, a US official said.

Obama, on his first Asia tour, made the schedule change so he could meet the other 20 regional leaders on Saturday evening ahead of Sunday's official summit talks, a White House official said.

"We had built into the schedule a bit of extra time and some downtime, and the president decided very early this morning that he thought it was more important to get to APEC earlier and be part of the discussions tonight," said White House spokesman Robert Gibbs.

The change of plans also appeared likely to rescue a hallowed tradition of APEC summits - the group photo of the 21 regional leaders in colourful, local costume.

Obama's week-long tour of Asia earlier had to be compressed by a day after the president travelled to Texas to attend Tuesday's memorial service for the 13 victims of a shooting rampage at the Fort Hood military base.

This led APEC organisers to say they would scrap the traditional group photo Saturday evening of national leaders including China's President Hu Jintao and Russian President Dmitry Medvedev.

In his Tokyo speech, Obama hinted at the change, which did not force him to scrap any official engagements in Tokyo, saying about the APEC meet: "I look forward to participating in that forum this evening."

The annual APEC photo has seen leaders in a variety of costumes, from leather bomber jackets in Seattle in 1993 to calf-length silk tunics in Hanoi in 2006, and Peruvian ponchos in Lima last year.

For this year's APEC photo, the designated costume had been a long-sleeved linen shirt inspired by the blend of Chinese, Malay and Indian culture found in Singapore, organisers said.