Their machines are being challenged to carry out a series of disaster-related tasks in the shortest time possible.

The US Department of Defence's Darpa research unit will host the event on Friday and Saturday at a location close to Los Angeles, California.

A team from Google was a favourite to win, but has quit the contest as Google had concerns about being linked to a military-backed event, even though it is has a "humanitarian" theme.

Two tries

The Darpa Robotics Challenge (DRC) involves eight tasks:

Driving a car
Getting out of the car
Opening and walking through a door
Opening a valve
Using a drill to cut a hole drawn onto a wall
Crossing a debris-filled terrain - either by clearing a path for itself or walking over the rubble
Climbing up steps
A mystery event, that will only be disclosed to the teams on Friday

Each team will be given two attempts to complete the run.

The crews can provide remote guidance - for example helping their robot identify the valve - but cannot control specific movements.

While the tasks are similar to those in the last round, contestants now only have an hour to complete the circuit.

The competitors will get a point for each task their robot completes and those with equal scores will be ranked according to their finish times.

The finalists include teams from the US, South Korea, Japan, Germany and Italy.