Mayor Nutter is among nearly 200 mayors expected to attend a national conference that begins tomorrow in Providence, R.I., even though Vice President Biden and other members of the Obama administration have pulled out because of a planned picket by Providence firefighters.

The union and city have been in a contract dispute for nearly a decade, with the latest pact struck in 2000.

The threatened demonstration at the annual meeting of the U.S. Conference of Mayors is the firefighters' latest effort to embarrass Mayor David N. Cicilline. To close a $17 million budget deficit, he has proposed changing health and pension benefits for the union's 500 members.

Members of the Obama administration had been expected to participate on panels and answer questions on the federal stimulus package. Besides Biden, scheduled speakers included Housing and Urban Development Secretary Shaun Donovan, Labor Secretary Hilda Solis, and Attorney General Eric H. Holder.

But on Friday, the White House announced that it would respect a picket line by Local 799 of the International Association of Fire Fighters, which plans to demonstrate throughout the four-day conference.

In Philadelphia, Nutter is negotiating an agreement with Local 22 of the union, whose city contract expires June 30. The two sides, which rely on an arbitration panel to reach terms, are not expected to begin talks in earnest until September.

Told that Nutter would attend the conference, Local 22 president Brian McBride said: "Shame on him. He should honor the picket line and not go. He should save the taxpayers some money and the expense of him and his staff going to Providence, R.I."

As of yesterday afternoon, just one mayor, from Burlington, Vt., was rumored to have canceled his participation, said Elena Temple, a spokeswoman for the mayors group.

Nutter, after returning from a news conference this afternoon in New York, was expected to leave for Providence tonight with legislative-affairs aide Tumar Alexander. Allan Frank, Philadelphia's chief information officer, was also expected to attend to participate in a workshop.

According to the conference agenda, Nutter is scheduled to speak on three panels, concerning green jobs, climate protection, and the reentry of ex-offenders into society.

"It couldn't possibly be shameful that the mayor would attend a conference with his counterparts to discuss the work that is being done in cities across the country," Nutter spokesman Doug Oliver said.

"Mayor Nutter, as well as other mayors, are on the front line of this financial crisis and will be leading the economic recovery," he continued. "The conference is one way to share best practices as we all work to weather the storm and minimize long-term negative effects."