The 6T will mark a major launch for OnePlus, which is currently trying to push into the mainstream and take on phones like the iPhone.
But Apple announced that it would be holding its latest event on 30 October, in New York City. That happened to be the same time and location as the OnePlus event, forcing it to change its schedule.
OnePlus said that it had wondered what to do about the clash, which was revealed just days before the event is due to happen.
"We know the entire industry and all media will be holding their breath," wrote CEO Pete Lau on the company's message boards. "So, imagine how we felt when we learned the date of their latest event.
"One minute, we were preparing for our greatest and most exciting launch event yet. The next, we were posed with a difficult question: 'What do we do now?'"
Mr Lau said the company had consulted with members of the media and tried to understand how to make sure that people watched it. But OnePlus eventually concluded that it would not be possible to ensure the new phone would get enough attention.
"We have to remain realistic," he wrote. "We have only just begun our journey and cannot afford to let one of the most important products in our history be affected by another great product launch."
OnePlus invites its customers to come along to its events, and said that it would happily pay for changes that people were forced to make in order to attend, covering flights and hotels. Its team would be getting in touch with ticketholders, Mr Lau said.
Other launch events that allow fans to watch livestreams together around the world – like the one held in London – will have their date adjusted a day forward accordingly.
Apple's event on the 30th is unchanged. The company is expected to show off new iPads and Macs – and the event is notable for being one of the few Apple events that takes place outside of its home in California.
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