The local organizer, MNC media group, said it was not possible to cancel the contest or move the location, and that the government had pledged to provide security for the event.
"I think there is a misunderstanding," Hary Tanoesoedibjo, head of MNC, told reporters Wednesday in Bali. "I assure that there will be nothing that runs against our culture. I would not accept if there was a bikini show."
The chairwoman of the Miss World Organization, Julia Morley, earlier confirmed that none of the contestants would wear a bikini.
The competition will be held partly on Bali, with the final round set for Sept. 28 on the outskirts of Jakarta.
"The contest will not be different from other beauty pageants in Indonesia," said Budi Rusmanto, an organizer in Jakarta. "The only difference is the participants."
Rejection of the event has come not only from hard-line groups, but also from the country's most influential clerics' group, the Indonesia Ulema Council, whose fatwas, or edicts, are followed by many devoted Muslims.
Last week, the council urged the government to cancel the contest, saying the exposure of skin by women in such a competition violates Islamic teachings, even after organizers agreed to cut the bikini competition and instead outfit contestants in more conservative sarongs.
Most Muslims in Indonesia, a secular country of 240 million people and the world's most populous Islamic country, are moderate, but a small extremist fringe has become more vocal in recent years.
On Wednesday, hundreds of protesters took to the streets in Surabaya, Indonesia's second-largest city, and Bandung, the West Java capital, while on Tuesday hundreds rallied in Jakarta.
The Islamic Defenders Front, a hard-line group with a long record of vandalizing nightspots, hurling stones at Western embassies and attacking rival religious groups, has pledged to disrupt the event if it is held in Indonesia.
Bali police spokesman Col. Hariadi said there have been no signs of security threats and that police are guarding all airports and seaports on the tourist island.
"Security around locations set for activities of the event and the participants as well will be optimized," said Hariadi, who uses one name.