A 17-year-old boy has been refused bail after allegedly threatening a woman and two children before leading police on a 100km chase in western NSW.

Police were called to a carpark on Montkeila Road, Walgett, around 691km from Sydney, yesterday afternoon.

A 35-year-old woman had her car allegedly stolen by the teenage boy.

She told police she and her two children, aged two and four, were threatened by the boy, who was allegedly armed with a machete and demanded she hand him the keys to her car.

Police then saw the car travelling south on the Castlereagh Highway towards Coonamble, where police attempted to stop the vehicle.

The teenage boy refused to stop, so a pursuit was initiated that lasted 100km.

It ended when the police deployed road spikes around 20km north of Coonamble, and the 17-year-old was subsequently arrested.

He was taken to Walgett Police Station and charged with multiple offences, including armed robbery, aggravated assault with intent to take and drive a motor vehicle with a weapon, hinder or resisting police.

He appeared before a Children’s Court today.