"We won't do a big, crowded convention per se", Trump said.
Despite urges to ignore them, Trump was closely watching as several Republican lawmakers said they weren't going to Jacksonville or were considering not going, a person familiar said.
On June 3, Mr Trump lambasted the governor of North Carolina for being unwilling to let the Republican party hold its national convention there.
Instead, the party will hold official business in North Carolina, perhaps just one day, Trump indicated, with a skeletal group of attendees.
For the Florida part of the GOP convention, there will be tele- and online rallies instead of a physical convention. "It's hard for us to say we're going to have a lot of people packed in a room and then other people shouldn't do it".
United Kingdom government secures 90 million doses of Covid-19 vaccines
The trial showed that volunteers given two doses of the vaccine produced virus-neutralizing antibodies, similar to the USA trial. In early June, the team was forced to begin trials of the vaccine in Brazil and South Africa, where cases were rising quickly.
His decision Thursday marks a complete reversal after insisting for months that an in-person acceptance speech be delivered before a massive crowd.
Events in Charlotte, North Carolina, will still be held.
"I could see the media saying 'Oh, this is very unsafe, '" Mr Trump added. "We have to be careful, and we have to set an example". Trump and his advisers feared that going forward with big parties and "infomercial" programming in Florida would ultimately backfire on the president.
Trump was wary of having sparse attendance at the convention. "I claimed you will find very little extra critical in our region than holding our people today risk-free, whether or not it really is from the China virus or the radical remaining mob".
Jacksonville Mayor Lenny Curry, who is a former chair of the Florida Republican Party, said he appreciated Trump "putting health and public safety first". Only 336 delegates will be allowed to participate in Charlotte under extraordinary procedures approved last month by the Republican National Committee.
A Republican official in Jacksonville explained to CNN that a trip for local company leaders to Tampa following 7 days - to meet up with with men and women to discover about their 2012 conference encounter - was abruptly canceled on Wednesday.