FILE PHOTO: Singapore's national flags are displayed from an apartment block during National Day in central Singapore August 9, 2011. REUTERS/Kevin Lam

SINGAPORE (Reuters) - Singapore said on Monday it will hold a presidential election on Sept. 23 if more than one candidate is nominated to run for the largely ceremonial post that has been reserved for someone from the ethnic Malay community.

Under a constitutional amendment passed by multi-ethnic Singapore’s parliament in November, the post will be reserved for candidates from a particular ethnic group if no one from that group has been president for five straight six-year terms.

If there is only one candidate on nomination day, Sept. 13, that person will become president. If there is more than one, the election will be held on Sept. 23, the Elections Department said.

The city-state has a population of 5.6 million, with 3.9 million of them residents, including both citizens and permanent residents, according to the Department of Statistics.

Among residents, 2.9 million are ethnic Chinese, 526,000 ethnic Malay and 357,000 ethnic Indian, and authorities are keen to promote unity and social harmony.

The president mostly performs ceremonial duties but wields veto power over the use of financial reserves and the appointment of key civil servants.

The current president, Tony Tan, is due to finish his term later this week, having been elected in 2011.