With the Covid-19 circuit-breaker measures extended to June 1, the Singapore Turf Club (STC) will reschedule the $1.5 million Kranji Mile and the $800,000 Lion City Cup to a later date.
The two Kranji feature races - over 1,600m and 1,200m respectively - were slated for May 23.
The Kranji Mile will be closed to international participation. Only Singapore-based horses are eligible for the race.
"The measures are in line with the Ministry of Health's advisory on 'Strong National Push to Stem Spread of Covid-19'," said the STC.
Earlier, the $1 million Group 1 Singapore Derby (1,800m) scheduled for April 18 was also postponed.
The Lion City Cup is the marquee domestic Group 1 sprint, after the discontinuation of the $1 million International Group 1 KrisFlyer International Sprint over the same distance in 2016.
The Kranji Mile was inaugurated as an invitational domestic Group 1 race two years ago, with the objective of becoming an International Group race, in a bid to restore international racing in Singapore.
The STC raised the prize money to $1.5 million, making it the new richest local race, overtaking the $1.35 million Singapore Gold Cup over 2,000m. The Gold Cup purse was reduced to $1 million last year.
Towards the end of last year, the Kranji Mile was accorded International Group 3 status by the Asian Racing Federation.
Hong Kong's Southern Legend captured the Kranji Mile the last two years and his connections were looking forward to a hat-trick.
But news of the race being restricted to Singapore horses left his trainer, Caspar Fownes, and owner, Boniface Ho, disappointed.
Said Fownes: "We wanted to have a go at the three-peat. He's a tough horse with a lot of heart. But, under the circumstances, we totally understand." The gelding won Hong Kong's Champions Mile yesterday, beating two-time Horse of the Year Beauty Generation by a short head.