The public spat between organizers for the Mawazine Festival and the Justice and Development Party, or PJD, the country's largest authorized Islamist group, illustrates the growing rift between Morocco's Western-leaning authorities and the more conservative Muslim movements that are on the rise in the North African kingdom.
"This singer is famous for his homosexual behaviour and for advocating it," said Mustapha Ramid, a leader and spokesman for the PJD, the biggest opposition party with 40 lawmakers in parliament.
"We're a rather open party, but promoting homosexuality is completely unacceptable," Ramid told The Associated Press in a phone interview, saying homosexuality is against Muslim values. Ramid feared the singer would "encourage the phenomenon" and be a bad influence for Morocco's youth.
Like nearly all Arab and Muslim countries, Morocco is officially hostile to homosexuality. Homosexual practices are a crime punishable by fines and prison sentences of six months to three years. But in practice, such penalties are almost never applied, and Morocco has a long history of leniency toward homosexuality or other practices forbidden by Islam, like drinking alcohol.
Despite the rise of Islamism in recent years, this country is considered among the most tolerant in the Arab world, and several prominent gay intellectuals or artists have lived here, including the late French fashion designer Yves Saint-Laurent and the American writer Paul Bowles.
Moroccan officials dismissed the calls to ban Elton John from performing.
"We deal with artists and intellectuals for what they do, without taking into account their private life," Mawazine Festival organizer El Hassan Neffali told reporters. "Somebody's private life is one thing, and their art or creative activities are another."
Elton John is expected to draw tens of thousands of viewers Wednesday night during his free concert, to be held in an upscale neighbourhood of Rabat, the capital. Seven other stages are set throughout the town. Other singers performing during this year's May 21-29 festival include Sting, Mika and Carlos Santana, along with a host of Arab music stars.
In an apparent move to defuse possible tensions, Elton John is the only artist booked for this year's festival who isn't scheduled to meet with the local media.
In Egypt, tentative plans to schedule the British pop star were cancelled earlier this month. Mounir el-Wasimi, the head of the Egyptian musicians union, released a statement in Egyptian media warning against the artist's possible visit because "he is a symbol of homosexuals in the world."
El-Wasimi cited an interview given by Elton John to America's Parade Magazine in February, where the singer said Jesus was "a compassionate, super-intelligent gay man who understood human problems" and said Middle Eastern countries mistreated lesbians.
El-Wasimi said these statements were unacceptable because Muslims consider Jesus a prophet.
In London, Elton John's publicist said the singer would make no comment.
The PJD and other conservatives have regularly criticized the Mawazine Festival, saying it promotes promiscuity and artists who don't abide by Muslim morals. It also blames the festival season for distracting students from their end of the year exams.
The free concerts usually draw huge crowds. Eleven people were killed and about 30 injured last year when a stampede broke out at the end of a concert. Organizers say they have boosted security this year.
Abdellah Taia, a Moroccan writer and the country's most prominent gay advocate, said that while Moroccan gays continue to suffer from abuse, the country is evolving faster than any other in the Arab world. He noted that even the official Le Matin newspaper, considered the mouthpiece for the royal palace, came out to strongly support Elton John's visit.
The first gay magazine in the Arab world, called Mithly, came out last month in Morocco, though it is sold under the counter because it didn't get an official distribution license. The gay rights group that publishes it - one of the first in any Arab country - is based in neighbouring Spain.
Its first edition announced Elton John's Moroccan concert as a major symbol.
De Montesquiou contributed from Paris. With files from Maamoun Youssef from Cairo.