Chief Superintendent Brian Maguire said: "The Army technical officer has confirmed this was a viable device capable of causing death or serious injury.
"We are investigating the possibility that this was an under-car booby-trap device."
Read Ken Reid's blog: Bombing shock
'Loud bang'
The 38-year-old policeman's girlfriend was taken to the Royal Victoria Hospital for minor injuries and was later discharged.
She was reversing a red MX5 sports car out of the drive of the semi-detached house at Kingsdale Park at 7.30am when there was an explosion under the front of the car.
One neighbour said they had been woken by "a loud bang".
The bomb was fitted under the front passenger side of the two-seater car and Mr Maguire said: "Had a person been sitting in the passenger side, we may be talking about a fatality here today."
He declined to point the finger of blame at any organisation, saying: "Investigations are at a very early stage and all avenues are being explored."
He added that police officers had, for some time, been advised to check under their own vehicles.
"We are aware there is a serious threat and that has been the case for some time."
He confirmed that the woman had no direct link, past or present, with the police service but said detectives were investigating whether a serving officer was the intended target of the bomb.
Kingsdale Park remained sealed off for hours while forensic experts combed the area for clues.
The soft-top car remained behind screens half in the drive and half across the road.
'Evil act'
First Minister Peter Robinson said the attack was an "evil act designed to murder a police officer."
"I condemn it in the strongest possible terms."
"Those responsible have nothing to offer and must face the full rigours of the law."
"Undoubtedly those responsible are determined that Northern Ireland should be plunged back into the dark days of the past. They will not succeed."
The attack comes amid ongoing negotiations between Stormont and Prime Minister Gordon Brown over the stalled devolution of policing powers.
Arriving back in Northern Ireland after cutting short an engagement in London, the First Minister said the murder bid highlighted the importance of securing the resources to tackle the dissident republican threat.
Deputy First Minister Martin McGuinness said he condemned an attack which had obviously been intended to kill.
He said: "The vast majority of people want a future together in peace. The people of Ireland overwhelmingly support the peace process. They want the political institutions and progress to continue.
"Attempts like this to derail the peace process must not be allowed to succeed."
Policing Board member Ian Paisley Junior has also condemned the attack.
"This is a very serious development, it clearly shows the intent of those responsible."
"If it turns out to be dissident republicans, it confirms the view that they're prepared to go to any length to either kill a police officer or someone else in the community to make their point," he said.
East Belfast MLA and Ulster Unionist Party leader Sir Reg Empey said: "This is a quiet residential area and if it is the case of a police officer being targeted, I think it is a very serious development."
Police Federation chairman Terry Spence also condemned as cowardly and reckless the attack.
"All police officers and the wider police family must be vigilant about their personal security. Today's attempt to kill an officer was fortunately unsuccessful but we must be on our guard," he said.
Policing Board chairman Barry Gilligan said the victim was lucky not to be injured.
"They must not be allowed to inflict their vile terror on our community and I would urge anyone with information to pass it to the police."
Security Minister Paul Goggins said the attack was repulsive.
"News of this attack will repulse people across Northern Ireland. The remarkable progress that Northern Ireland has made over the past decade will not be derailed by criminals operating under the cover of darkness."
