The announcement means no fans will be allowed at the horse racing in Goodwood, the two Bob Willis Trophy matches at the Kia Oval and Edgbaston, and the Crucible theatre for the World Snooker Championships from Saturday.
The government had announced the pilots to stress-test its guidance on the return of fans to elite sports events.
The Prime Minister said planned re-openings for August 1 will be postponed for a fortnight.
The U-turn will affect racegoers who had planned to attend the final day of the Goodwood Festival.
The Sussex Downs were due to welcome a crowd of 5,000 on Saturday, which would have been the first time racegoers have been allowed on a racecourse since March.
It is understood Premier League clubs had been hoping to admit supporters at pre-season friendlies next month on a socially-distanced basis.
Boris Johnson told a Downing Street briefing: "With those numbers creeping up, our assessment is that we should squeeze that brake pedal... in order to keep the virus under control.
"On Saturday August 1, you'll remember we had hoped to reopen a number of the higher-risk settings that had remained closed and today I'm saying we're postponing those changes for at least a fortnight.
"That means until August 15 at the earliest casinos, bowling alleys, skating rinks and the remaining close-contact services must remain closed.
"Indoor performances will not resume, pilots of larger gatherings in sports venues and conference centres will not take place, and wedding receptions of up to 30 people will not be permitted."
Culture Secretary Oliver Dowden MP tweeted that the government will be working for a "safe return ASAP" for fans.
In response to the cancellation of the planned return of spectators to Goodwood, a joint statement was released from Goodwood racecourse, the British Horseracing Authority and the Racecourse Association.
It said: "The government has informed racing's leaders in the past hour that it has withdrawn permission for a pilot event involving customers to proceed at Goodwood tomorrow.
"The racing on Saturday will continue behind closed doors as it has on the earlier days of the Festival.
"We understand that concern about the national infection rate is the primary reason, and as a result all pilots of larger crowds in sporting venues will be postponed until at least August 15."
The two-day cricket clash between Surrey and Middlesex, which started last Sunday, had signalled the return of fans to some sporting events, and two more county friendlies also saw spectators through the gates.
A spokesperson for the ECB said: "We understand this is disappointing for supporters who have waited a long time to see their clubs in action and were looking forward to attending pilot events at the Kia Oval and Edgbaston this weekend.
"However, we understand the reasons the government has made this decision, and remain ready to work with them to ensure supporters can safely return to stadiums when government advice allows.
"We are pleased the Bob Willis Trophy will still begin this weekend behind closed doors, and fans will be able to watch their teams in action through the online streams being provided."
The World Snooker Championships was the only indoor event among the three pilots.
The tournament began on Friday with fans in attendance, with further spectators now missing out on attending the majority of the 17-day event.
The government's plans to allow fans inside the Crucible theatre had already been criticised by five-time world snooker champion Ronnie O'Sullivan and qualifier Anthony Hamilton.
O'Sullivan said earlier this week the players were being treated like "lab rats" and claimed anyone unconcerned by the decision to allow some spectators into the event must have a "death wish".
Hamilton, a 49-year-old qualifier who suffers from asthma, had withdrawn from the tournament after describing the decision to allow a limited audience as "ridiculous".
The tournament is set to end on August 16, with current restrictions on fans in place until August 15 at the earliest.