US builders cut their spending on construction projects in September, the second straight monthly decline.

The Commerce Department says total construction spending fell 0.7 per cent in September to a seasonally adjusted annual rate of $US1.15 trillion ($A1.50 trillion).

Private construction slipped 0.2 per cent as construction spending on factories, commercial spaces and utilities declined. Gains in home construction offset some of this decrease.

But government-backed construction dropped 0.9 per cent last month. Over the past 12 months, US government construction spending has slumped 7.8 per cent – a decline equal to nearly $US23 billion ($A30 billion). In September, spending on school buildings fell 1.1 per cent, while sewage projects plunged 5.4 per cent, transportation spending fell 0.9 per cent and park-related building decreased 3.2 per cent.