TRENTON — Gov. Chris Christie's administration has filed a formal notice that it will appeal a court ruling that it broke the law by slashing this year's payment into New Jersey's public worker pension system.

A state Superior Court judge late last month sided with public unions who sued Gov. Chris Christie to force him to restore $1.57 billion left out of the current state budget, which runs through June 30. In the ruling, Judge Mary Jacobson knocked the administration for its "succession of empty promises."

Christie's administration announced plans to appeal immediately after the ruling, calling it "liberal judicial activism."

According to Friday's motion, Christie will appeal to the state appellate division rather than the state Supreme Court — a signal that he's not interested in resolving the case quickly, experts say.

Richard Harris, a political science professor at Rutgers University-Camden, said after the February ruling that Christie would be looking to buy time as he eyes the 2016 Republican nomination for president.

Appealing first to the appellate court will give Christie two bites at the apple, said Matthew Hale, a political science professor at Seton Hall University. He added that the longer and harder Christie fights this, the better he looks to presidential primary voters in Iowa.

"He wants to play this out as long as he can," Hale said.

The administration also asked the court for an extension until the end of the month to file the appeal.

A spokesman for Christie did not immediately return a message seeking comment. A spokesman for the state Attorney General's Office declined comment.

Jacobson's ruling ordered Christie to work with the Legislature to make the full payment required under a 2011 pension reform law. Lawmakers have said they don't know where they would come up with the cash before the end of the fiscal year on June 30.

Public worker unions are already lining up lawsuits based on Christie's proposed budget for the fiscal year that begins July 1, which includes a $1.3 billion pension payment -- less than half of the $3.07 billion required by law.

"It's the stall tactic we completely expected from this administration," said Patrick Colligan, president of the New Jersey State Policemen's Benevolent Association. "Whatever the slowest way to slog through these courts is how we fully expect the Christie administration to handle this. That's why we sued him for 2016 in anticipation."

The PBA and New Jersey State Firefighters' Mutual Benevolent Association filed a new complaint today in Superior Court for the fiscal year beginning July 1.

The disputes stem from a 2011 pension reform law that Christie hailed as a signature achievement during his first term as governor. As part of that deal, he agreed to bring some consistency to the state's uneven record on making pension contributions by ramping up to the annual contribution recommended by actuaries.

Workers were required to pay more into the system, cost-of-living increases were suspended and the retirement age was raised. In the lawsuits, unions argued they kept up their end of the deal, while the state shorted the system.

Lawyers for the state, meanwhile, said Christie wasn't bound to what it argued was an unconstitutional law.

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Samantha Marcus may be reached at smarcus@njadvancemedia.com . Follow her on Twitter @samanthamarcus. Find NJ.com Politics on Facebook.