"We have worked a deal out with Parker's people and Andy signed the contract earlier this week, but it was all subject to the sanction," Arum told ESPN.com.
"We got the sanction and it's a done deal. I met with Dean on Monday. He was in California before he went on to the Puerto Rico for the convention.
"My (matchmakers) think Andy has a hell of a shot. The kid is pumped because apparently he's sparred with Parker and more than held his own. I've seen some of Parker's fights on YouTube clips. He's a tremendous puncher but he doesn't look to me to be particularly fast and Andy is a very fast heavyweight."
10 things you must know about Andy Ruiz
The fight faced a possible delay after the December 10 date clashed with another fight featuring middleweight titleholder Gennady Golovkin, who is trained by Abel Sanchez - the same trainer of Ruiz.
However Golovkin's next title defence has been moved to early 2017.
THE VENUE
American boxing outlets are reporting the Parker-Ruiz fight will be at Auckland's Vector Arena but Duco Events are yet to confirm that.
The indoor stadium in the Auckland CBD is not booked on the December 10 date the World Boxing Organisation has ordered the Parker-Ruiz confrontation happen.
Nor is Eden Park or Mt Smart Stadium.
The confirmation of the fight, potentially the biggest sporting event in New Zealand's history, broke this morning out of the WBO's annual convention taking place in Puerto Rico.
Duco's Dean Lonergan is at the convention along with Ruiz's handlers, led by veteran American promoter Bob Arum.
Parker's trainer Kevin Barry has re-tweeted a tweet from his son Taylor, who is also part of the Parker camp, saying: "It's on!". Taylor Barry also tweeted the New Zealand Herald's breaking news story this morning about the fight.
Lonergan is yet to talk publicly but speculation will now centre on which venue will host the fight.
Vector would only be able to house around 10,000 spectators in a boxing environment. Eden Park and Mt Smart could definitely take a bigger crowd but the weather factor must also be considered by Duco.
If Parker beats Ruiz, New Zealand may then host Parker's first defence of the WBO belt.
Out of the same Puerto Rican conference, the WBO followed up its earlier decision by adding that it had "ordered" that the winner of the Parker-Ruiz fight must defend the belt against Britain's former world champion David Haye.
Lonergan told fightingnews.com that he had no issues with those conditions.
"We are happy with that," he said.
In its report confirming news of the Parker-Ruiz bout, American Boxing Scene website reported the fight would be at Vector Arena.
The WBO had raised the spectre of a four-way box-off, with Anthony Joshua and Wladimir Klitschko the other pair in the mix but according to ESPN they have agreed to a Parker-Ruiz Jr fight instead. It would be Parker's fifth fight of the year.
FIGHTING WORDS
A scrap against 27-year-old Ruiz Jr is almost guaranteed to be exciting going by the undefeated Mexican-American's style and recent comments.
The pair sparred together in Las Vegas three years ago, with Ruiz Jr initially getting the better of Parker, 24, who said recently his mouth was so sore he couldn't eat for days afterwards.
"I was kind of surprised [to hear that] because it didn't seem like he was really hurt in the sparring," Ruiz Jr said. "The first time we sparred there were some good exchanges. He's pretty fast and he likes to throw combinations as well. We were both exchanging and I guess I got there first. I kind of dazed him. I rocked him pretty good.
"In his last fight [against Alexander Dimitrenko] he beat this guy fast. But from his other fights I don't think he looked that good. My pressure and the speed of working the body and head at the same time - I think... I can do what I did in sparring.
"This is the best fight I could have for the world title."
Joseph Parker's route to a world championship
•There are four world boxing championship organisations - the WBA, WBF, IBF and WBO
•Joseph Parker was previously chasing the IBF belt held by Anthony Joshua
•But Joshua's promoters have bumped him down their list for a November fight because they want to take on Vladimir Klitchko instead
•Duco Events have been eyeing the WBO belt as the holder Tyson Fury was stripped of it
•Parker and American Mexican Andy Ruiz are the highest ranked available contenders
•That fight could happen this summer in Auckland
