Robert Philbin, a spokesman for Mayor Linda Thompson, confirmed the news that Unkovic submitted his letter of resignation to the Commonwealth Court. Unkovic has been unavailable for comment.
"It's unfortunate," Philbin said. "(David) has done an excellent job moving the city recovery process forward."
Philbin said he did not know the reason for the move. A call to the Commonwealth Court communications was not immediately returned.
Kevin Harley, a spokesman for Gov. Tom Corbett, called Unkovic's decision "unexpected and unfortunate."
"Working with DCED, the governor will move quickly to recommend a receiver to the Commonwealth Court," he said, referring to the Department of Community and Economic Development. "The Corbett administration remains committed toward working for financial stability for the city of Harrisburg."
DCED nominated Unkovic to the post. He had been chief counsel with the agency.
Corbett was told via a letter, Harley said.
"We will move as expeditiously as we can to find a competent receiver," he added. "We understand the time constraints we're working under."
"The mayor is moving forward with the plan," Philbin said. "We're moving forward with executing a plan. A quick replacement would be to everybody's benefit."
It is unknown what impact this decision will have on asset negotiations and a final recovery plan. A Commonwealth Court judge earlier this month approved a preliminary plan proposed by Unkovic.
He was appointed by the court in December.
Unkovic said he planned to amend the plan. He first wanted to determine the value of city assets before negotiating debt payments with creditors.
His proposal called for the sale and lease of the incinerator and parking facilities. In addition to the incinerator and parking, Unkovic also included in his plan a recommendation to look at management and operation of the water and wastewater assets.
His goal was to determine the valuation of those assets this spring and to come back in June with a more comprehensive plan that also included favorable concessions from the city's three unions who have contracts in place through 2014, 2015 and 2016.
He said his goal was to have deals worked out with the unions, asset deals in place and negotiations with creditors ironed out before coming back to the court with an amended recovery plan.
Meanwhile, the city today announced the hiring of a business administrator and chief of staff.
"Mr. Unkovic was our last hope to get the City back on track. He spent hundreds of hours researching the issues and communicating with all of the players involved. He was working toward an equitable solution and in the interest of the residents," Councilwoman Patty Kim said in an emailed statement. "The departure of Unkovic is a huge blow to Harrisburg."
Unkovic's resignation is a major setback to the recovery process, Harrisburg Hope President Alan Kennedy-Shaffer said in a statement.
Harrisburg Hope is a grassroots community organization.
"Getting Harrisburg out of debt is going to take concessions from creditors, sacrifices from residents and creative solutions on all sides," he said. "David Unkovic was listening to the community. He was leading the way — slowly — toward a solution to the debt crisis. Without leadership, the prospect of bankruptcy for Harrisburg becomes much greater."
"He will be an enormous help," Philbin said of that move.
Editor's note: This item was modified from its previous version to add comments from Harrisburg Hope President Alan Kennedy-Shaffer.