Heads of state posing for photos in the traditional attire of the host nation represent one of the most distinct and memorable attributes of the Asia-Pacific Economic Cooperation summit held each year. In Chile, presidents and prime ministers donned flowing ponchos. In Vietnam it was silk tunics.

This year, 21 leaders are gathering in Honolulu, inspiring visions of Chinese President Hu Jintao and President Barack Obama in aloha shirts. But it’s not clear whether APEC leaders will observe the custom this time as the White House remains mum on the issue.

The attire has been the subject of great speculation, as locals are anxious to see whether world leaders will don colorful, floral aloha shirts. Obama himself stoked speculation when he announced two years ago that he would host the 2011 meeting in the city of his birth.

"I look forward to seeing you all decked out in flowered shirts and grass skirts," he told his counterparts, who that year wore silk tunic shirts with mandarin collars in Singapore.

The White House hasn’t disclosed what it plans to ask delegates to wear for Sunday’s group photo, and didn’t respond to a request for comment.

But last year, host nation Japan skipped the ritual for the first time. Officials cited a tight schedule and said tight-fitting traditional kimonos might not be suitable for a photo session. The leaders instead wore jackets, slacks and shirts without neckties.

DeSoto Brown, historian and co-author of the book "The Art of the Aloha Shirt," said it would be disappointing if APEC leaders didn’t wear Hawaii’s signature garb. Brown said he could see that some people might not view aloha shirts as businesslike because they’re often associated with being on vacation. But he noted that in Hawaii they’re worn every day by high-level businessmen.

"Aloha shirts are truly from Hawaii. They were invented here and are known worldwide," Brown said. "And since President Obama is from Hawaii, it would be even more appropriate that everyone at APEC should have their photo taken wearing what he is already very familiar with."

There is precedent for world leaders going local in Hawaii. President Bill Clinton sported a baby blue aloha shirt with pink flowers to give a speech in Waikiki in 1993. Hu wore a brown and green patterned one to a luncheon with Hawaii’s governor when he stopped in Honolulu as China’s vice president in 2002. Shortly after winning the Republican nomination for president in 1960, Richard Nixon campaigned in Hilo wearing a hibiscus-patterned shirt.

The APEC tradition began in 1993, when Clinton handed out bomber jackets for the leaders’ commemorative photo in Seattle.

Some leaders have appeared visibly uncomfortable in the costumes. Japanese Prime Minister Junichiro Koizumi kept smoothing out his royal blue jacket as he stepped out of his limo at the APEC summit in Shanghai in 2001. And he continued to adjust the jacket while posing with Chinese President Jiang Zemin.

But the custom can also break the ice. In Hanoi a normally dour and somber Hu beamed while posing in an ankle-length Vietnamese tunic in 2006, and Russian President Vladimir Putin joked cordially with President George W. Bush.