Mayor Mike Rawlings called Tuesday for an immediate suspension of lump-sum withdrawals from the Dallas Police and Fire Pension Fund.

The mayor's request, made in a strongly worded letter to the pension board, was the latest salvo in a high-stakes fracas between city leaders and its semi-independent public safety worker pension system. The troubled fund is headed toward insolvency by 2028, and its leaders are banking on a taxpayer bailout to save it.

Board Chairman Sam Friar said the mayor's letter "perturbed" him and took it as a possible prelude to legal action. But Rawlings said he wrote it to make his views clear.

"I don't believe the city is wanting to get into a legal action with the pension fund at this point," Rawlings said.

The lump-sum withdrawals have put the fund in a precarious position. They come from the fund's Deferred Retirement Option Program, known as DROP, which allows veteran officers and firefighters to "retire" in the eyes of the system and continue working. Meanwhile, the pension checks they would have received are credited to the DROP account and accrued, for years, interest of more than 8 percent. Retirees could also keep their money in the fund.

Hundreds of officers and firefighters became millionaires from the accruals. And the pension had no limits on withdrawals or deferrals, meaning DROP essentially became a guaranteed high-interest checking account, even in the worst of financial times.

The previous administration didn't believe the run on the bank would ever happen. When The Dallas Morning News asked then-administrator Richard Tettamant about the possibility in 2012, he replied that it wouldn't happen.

"This could happen to Bank of America or Fidelity Investments as well, but as with them, there would be no reason for people to do that," Tettamant said in an email. "The pension system has sufficient liquid assets to cover all DROP distribution requests."

More than $500 million has been withdrawn from the $1.5 billion fund this year. Most of it came after Aug. 11, when the pension fund proposed benefit cuts to help save it from insolvency caused by overvalued and risky real estate investments made by the previous administration.

Still, the current pension board, which includes four City Council members, unanimously decided not to restrict DROP withdrawals this year after hours of deliberations and legal advice given behind closed doors.

Pension board members believed they couldn't restrict the withdrawals forever and feared the backlash from police and firefighters when the restrictions were lifted. And they hoped that keeping DROP open would boost confidence in the fund.

Rawlings said he has spoken to the council representatives about his views. And in his letter, he chastised the board for its decision, saying it has not stopped the bleeding as hoped. Eventually, the fund's finances will be imperiled if officials have to sell off assets to pay out DROP withdrawals. Doing so would weaken the fund's ability to make money to pay benefits. Those who aren't in DROP wouldn't have much left for them.

"I feel I have an obligation to the young officers and firefighters of Dallas to make sure they don't end up on the short end of the stick on this pension fight," Rawlings said.

Friar said the board might reconsider restricting DROP withdrawals but wouldn't be able to do so on the mayor's 48-hour timetable.

He also said the letter contained "some misleading as well as erroneous information." He was annoyed that Rawlings quoted him in the letter slightly out of context to make a point.

Sam Friar, of the Dallas Fire-Rescue Department, and Chairman of the Board of the Dallas Police & Fire Pension System, listens during the Board of Trustees meeting at Dallas Police and Fire Pension System in Dallas, Thursday, Oct. 13, 2016. (Jae S. Lee / Staff Photographer)

Friar also faulted city leaders for failing to assuage members' fears. Pension officials had asked city officials to release a public statement expressing support for the fund and telling police and firefighters that the city had their backs.

If city officials had done so, Friar said, the money in DROP "would still be there."

"They have just as much fault about this money not being there," he said.

Dallas Fire Fighters Association President Jim McDade also blasted the mayor for the letter. He said the city needs to step up instead of throwing "gasoline on the fire."

"If the mayor believes that his letter will stop the 'run on the bank' he is wrong," McDade said in a written statement. "He just created a SPRINT to the bank."

But the price tag on any solution will be a doozy, and it won't be easy for city officials to make a commitment. Pension officials are asking for $1 billion. Rawlings has said the city doesn't want to pay that much and could ask for deeper cuts from the pension fund to make up the difference.

The full City Council will receive a briefing on the pension fund next week.

Council member Scott Griggs, a pension board member, said it's "past time" for the city to offer a solution.

"We need to find a solution in the middle that pays benefits and ensures public safety and ensures that we're able to improve our infrastructure," he said.

The mayor also said he expects the city "will participate in the long-term solution to this issue."

"Make no doubt about it," Rawlings said. "But right now, we're talking about an immediate crisis that we've got to deal with. They're talking about a long-term problem. I'm talking about a short-term problem."