Apa, who like most Sherpas goes by one name, first climbed the 29,035-foot (8,850-meter) mountain in 1989 and has repeated the feat almost every year since. His closest rival is fellow Sherpa guide Chhewang Nima, who has made 15 trips to the summit.
Apa announced Thursday his intention to make his 20th ascent in May. He and his fellow climbers - 17 other Sherpas and 12 Westerners - also plan to collect 7,000 kilograms (15,400 pounds) of garbage, a growing environmental problem on the Himalayan peak. They plan to pay porters hired by several expeditions to help bring down the refuse.
Apa, who moved to the United States in 2006 and lives in the Salt Lake City suburb of Draper, said he would scatter the ashes of Hillary at the summit. Hillary conquered Everest in 1953 with Sherpa Tenzing Norgay.
"I will pray for Hillary once I reach the summit," Apa told reporters in Katmandu.
He said he also wants to promote Nepal's campaign to attract half a million tourists in 2011, as the country recovers from years of instability and communist insurgency.
Apa grew up in the foothills of Everest and began carrying equipment and supplies for trekkers and mountaineers at age 12.
Sherpas were mostly yak herders and traders living in the Himalayas until Nepal opened its borders to tourists in 1950. Their stamina and knowledge of the mountains makes them expert guides and porters.