Prime Minister Lee Hsien Loong told parliament the move was part of measures to limit the inflow of foreign workers to "a level which is sustainable and which we can physically accommodate in Singapore in the long term".

Lee said the government would continue "full steam ahead" with building more public housing and improving transport infrastructure, but would hold off on less critical projects for one or two years.

The long-ruling People's Action Party has tightened migrant inflows since suffering its worst showing in a 2011 general election, in which the large foreigner presence was a big issue.

"The private sector, they make their decisions," Lee said.

But "the government, we are a significant part of the construction business, and we ask ourselves which government projects need to be built (and) which projects can be deferred," he said.

"We can spread out the demand for construction workers, and then you will be able to manage the total number of construction workers in Singapore."

Lee said among the projects to be deferred are an extension of the Gardens by the Bay botanical complex and a new science centre.

The deferred projects would reduce the number of foreign workers needed by about 20,000 to 30,000, he said.

Lee said the government would also monitor the inflow of foreign professional workers to ensure that Singaporeans get a fair chance at jobs in some fields.

Singapore's low birth rate prompted the government to grant an average of 18,500 new citizenships every year between 2008 to 2012 -- helping the population surge by 30 percent since 2004 to 5.4 million last year.

Out of a foreign population of 1.55 million, about 700,000 are mainly Asian work-permit holders employed in construction, marine industries and other sectors shunned by Singaporeans. Some 200,000 others work as domestic helpers.

Singaporeans have accused foreigners of competing with them for jobs, housing, schools, medical care and space on public transport.

Some have also complained that the rapid influx in previous years is eroding national identity.