BOSTON (AP) – The city police and firefighter unions are invoking no less an authority than John Kerry to encourage delegates to the Democratic National Convention to boycott Mayor Thomas Menino’s speeches and events.

At the top of a letter to be sent to each of the nearly 5,000 Democratic delegates next week, the leaders of the Boston Police Patrolmen’s Association and the city firefighter union included the words Kerry spoke when he refused to cross picketing union members last month: “‘I don’t cross picket lines. I never have,’ said John Kerry.”

The letter, which is signed by police union president Tom Nee and firefighter union president Nick DiMarino, asks convention delegates to honor picket lines that will be surrounding the 29 delegation welcome parties scheduled for Sunday, July 25, the night before the four-day convention begins.

“We also ask for your support and petition all delegates to boycott Mayor Menino’s address to the convention by walking out as he begins his speech or by not attending at all,” the letter reads. “We shall be protesting and picketing any reception, speech or party Mayor Menino hosts or attends during the convention.”

Kerry spoke the quote used in the letter to explain why he canceled a speech at the U.S. Conference of Mayors, which Menino was hosting. Menino responded later by calling Kerry’s campaign “small-minded and incompetent.”

On Saturday, Menino spokesman Seth Gitell said he didn’t object to the unions’ use of Kerry’s quote in the letter.

“Anybody may invoke whomever they wish,” he said.

A spokesman for Kerry’s campaign did not immediately return a call for comment.

City and union officials attended an investigation hearing before the state Joint Labor-Management Committee Friday that could ultimately lead to arbitration. During the meeting, the city said the ongoing dispute poses a clear threat to public safety if not resolved before the convention. The committee will meet Thursday to decide on the next step.

The union letter to delegates also seems to hint at good news for Kerry: a possible endorsement from the police association, which has endorsed only Republican presidential candidates in the past, including George H.W. Bush in his 1988 campaign against hometown Gov. Michael Dukakis.

After quoting Kerry’s vow not to cross picket lines, Nee and DiMarino wrote:

“This quote is from the man that with all our help can be and should be the next President of the United State, our very own Senator from Massachusetts, John Kerry.”

Nee denied that this sentence signified an endorsement for Kerry. He said that the union’s board will decide on an endorsement in August.

Firefighters, both locally and nationally, have long been strong Kerry supporters. The Boston police union endorsed Kerry in his 1996 Senate race, but has always backed Republicans for president.

The police, who made an average of $79,000 a year in 2002, have been operating without a contract for more than two years. The city has offered the union raises totaling 11.9 percent over four years. The union is asking for about 17 percent.

In June, their pickets delayed construction at the FleetCenter convention site for three days and disrupted the U.S. Conference of Mayors.

AP-ES-07-10-04 1614EDT