Walker was last seen (by police) when he fled into bush at Kaingaroa, east of Awanui, on September 26, after a brief Highway Patrol pursuit that began on State Highway 10 and ended on Duncan Road.
He was believed to have taken a rifle from his vehicle before fleeing.
Detective Sergeant Beatson said he had been working closely with members of Walker's family in an attempt to facilitate his safe surrender.
"This has involved discussions with his family and the provision of contact details so I can assist in safely bringing Mr Walker into police custody.
"To date Mr Walker has refused to hand himself in or make contact with police," he said.
The police reaction to "situations like these" were very much dictated by the actions or behaviour of the person involved, he added.
When Walker allegedly armed himself he escalated the situation from a simple traffic stop to something more dangerous.
The alleged incident was serious because of the introduction of a firearm to the scene.
"When you have an unarmed, sole officer on an isolated rural road with a person who is armed, the balance of power clearly swings in favour of the armed person," he said.
"As a result, in this specific incident, the Armed Offenders' Squad was called in an attempt to resolve the situation."
Because of Walker's alleged actions police have obtained a warrant for his arrest on a charge of using a firearm against a law enforcement officer. That warrant was current and remained in effect.
Detective Sergeant Beatson said Walker had a history of running from police, and was prepared to go to extreme lengths to avoid capture.
"While I agree Mr Walker may be no immediate danger to the public at large, he has certainly demonstrated a propensity to use firearms against police officers, and that was clearly demonstrated in this most recent incident," he said.
He urged members of the public who had information, or knew where Walker was, to pass that information to police, either by contacting him directly at the Kaitaia police station (phone 408-6500) or anonymously via Crimestoppers, 0800 555-111.
He also made a direct offer to Walker.
"I invite Mr Walker, wherever he is, to contact me as soon as possible so I can arrange his safe surrender," he said.
"If this is too difficult to do then I urge him to hand himself in, unarmed, at any police station in the country."
