They examined the device, which had the appearance of a mortar in a launcher tube, close to the Ballygomartin Road.
It was found by an off-duty police officer at around 7.15am on Friday. The alert was still ongoing in the early hours of Saturday morning.
Chief Inspector Emma Bond confirmed the target of the "mortar-type device" may have been the nearby New Barnsley Police Station.
The security alert forced residents from their homes and nearby primary schools had to shut on Friday.
"This is a very reckless attack and as a result of the evacuations of persons from homes and the closure of local primary schools has caused a significant degree of inconvenience to local community," she said.
Those who are behind this attack had very clear and, I believe, murderous intent.
Chief Inspector Emma Bond
She said it was "fortunate" that police had found the device, which was also spotted by a taxi driver.
"Had this device exploded then it would have had deadly and fatal consequences for an innocent member of the public, police service or anybody else," she added.
Ballygomartin Presbyterian Church Hall and the Whiterock Community Centre were opened to residents during the day.
Many people living in the area were allowed home on Friday night.
North Belfast DUP MLA William Humphrey said: "It is utterly appalling and disgusting that terrorists should put lives at risk by preparing such an attack. The fact that it was discovered close to two primary schools only adds to their recklessness.
"If this device had been deployed it could have caused indiscriminate slaughter, whether in the police station or among people living in houses on either side," he added.
I'm absolutely disgusted - as are most of the residents in this area. Nobody wants this disruption.
Pat Sheehan, Sinn Féin
Pat Sheehan, Sinn Féin MLA for West Belfast, said: "There are a large number of elderly people in Owenvale Nursing Home down there, whose lives are being disrupted by what is going on.
"There are women who are trying to get their children to school, whose lives are being disrupted. No-one wants it."
SDLP Councillor Colin Keenan said those behind the attempted bomb attack deserved "the condemnation of the whole community for the chaos and disruption they have caused".
"It is maddening to think people who are trying to go about their business are being disrupted and their lives but at risk due to the reckless and deranged mindset of a few," he said.
West Tyrone UUP MLA Ross Hussey also condemned the attack. He said this type of terrorism "which threatens law and order" cannot be tolerated.
Policing Board Chair Brian Rea said, although the target of the mortar device may have been police officers, whoever placed it also had complete disregard for the local community.
"It is only a matter of time before a member of the public is caught up in one of these reckless attacks and in this instance we are thankful for the vigilance of the police officer who spotted the device," he added.
I salute the PSNI and our security forces for their fortitude and bravery as they protect the entire community.
Ross Hussey, UUP
Detectives from the Major Investigation Team believe the device was brought to the Ballygomartin Road in a car or van between Thursday evening and Friday morning.
They appealed for anyone who saw suspicious activity in the area to contact them.
Meanwhile, police also dealt with a security alert in the Springfield Road area.
"It is not yet clear if both security alerts are linked," a police spokesperson said.
"We apologise for any inconvenience however our aim is to ensure the safety of the local community and to protect everyone. We would ask the public for their patience and understanding as this policing operation continues," the spokesperson added.
Part of the Ballygomartin Road remained closed between its junctions with Highcliff Gardens and Springmartin Road on Friday night.