After four years of futile talks, Mayor Nutter and union leaders representing the city's nonuniformed workers should meet with a neutral third party to help them reach a deal.

Their stalemate revolves around the ugly truth that the city's pension system will implode if it isn't fixed. It's bad for taxpayers, because pension payments can drain the city's coffers and force reductions in services while undermining the city's ability to borrow money. And it's bad for city workers, many of whom are hoping to retire on already small pension checks, if those checks dry up and they are forced to live out the rest of their years in poverty.

No one wants that, and therein lies the common ground that should help the city and the unions negotiate in earnest. The pension system can't be fixed unless both sides contribute more. This isn't fair to workers who have given their share while the city has skipped payments. But it is reality.

Unfortunately, neither side can grapple with reality, because each has become so mistrustful of the other. That's why they need a trusted person or persons to intervene and bring them together.

Labor leader and Nutter supporter Henry Nicholas has been lobbying for months to bring in an adult who can either put Nutter and union leaders in the same room or play Henry Kissinger and shuttle between them. The mayor and the unions should find a mutually respected broker, which shouldn't be that hard to do in a city of 1.5 million. They should consider someone who is familiar with the city's finances, such as Sam Katz, the chairman of the Pennsylvania Intergovernmental Cooperation Authority.

And each side should agree not to embarrass the other publicly any more than they already have. The March 14 City Council session, in which workers whistled and shouted until Council weakly recessed and cut off Nutter's budget address, was unacceptable.

But after Nutter asked the state Supreme Court to let him impose a deal on the city's blue-collar union, it's not surprising that workers in the building trades joined public employees in a remarkable show of solidarity. Both factions saw the mayor's request as a serious assault on collective bargaining. If Nutter's move was meant to be strategic, he needs to look at the chess board again and reconsider the lawsuit, because it could cost him the game.

Philadelphians are sick of the chest-thumping. Do your jobs, make a deal, and let the city move on.