Osama bin Laden’s first public message this year, in which he accused Pope Benedict XVI of complicity in a “new Crusade” against Islam, is raising fears here over security measures for the papal visit next month and the possibility of a terrorist attack.

The accusations directed at the pope have some in the city worried about security during the pontiff’s visit to America between April 15 and 20, which culminates in a Sunday, April 20, Mass at Yankee Stadium.

“When I heard the thing about bin Laden, I thought, this isn’t good,” Father Robert O’Connor of the Blessed Sacrament Church on the Upper West Side said. “It could stir up some wacko who wants to get attention.”

Spokesmen for the police department and the United States Secret Service, the two agencies that will be spearheading what is expected to be an enormous security operation when the pope arrives in the city April 18, wouldn’t say directly whether Mr. bin Laden’s message raised any red flags regarding security and the pope’s upcoming visit.

“The New York City Police Department has been working closely with the United States Secret Service to provide the highest level of protection possible for the pope during his visit to New York,” the police department’s top spokesman, Deputy Commissioner Paul Browne, said.

Still, several security experts and police sources said the bin Laden comments are undoubtedly garnering ample attention from police department brass.

“I think there is always enormous concern whenever the pope travels, and I’m sure bin Laden’s comments probably add to that,” the president of the Citizens Crime Commission, Richard Aborn, said. “Even though he may have not made a specific threat, some self appointed terrorist may want to carry out an attack.”

Even with the news of bin Laden’s message, confidence regarding the department’s planned security measures appears high. Several law enforcement experts said that the city’s police are widely regarded as the premier department in the world when it comes to guarding dignitaries.

In a move that Police Commissioner Raymond Kelly said would bolster security at high profile events in the city, such as papal visits, the police commissioner announced yesterday that the police and the United States Coast Guard signed an accord that will bolster their working relationship.

“This new agreement will help protect New York City’s critical infrastructure by giving the NYPD full authority to enforce the maritime safety and security zones that only the Coast Guard can establish,” Mr. Kelly said in a statement.

While the police are accustomed to guarding high-profile dignitaries, the pope’s arrival will create more security concerns than even that of a presidential visit due to the sheer number of people that will covet just a glimpse of the revered figure, security experts said.

A professor at John Jay College of Criminal Justice, Eugene O’Donnell, said that in the aftermath of a 1981 assassination attempt of Pope John Paul II in St. Peter’s Square in Vatican City, popes have been less accessible to the public.

In a measure that demonstrates tighter security than previous papal visits to New York, people who want to hear the pope speak publicly in Yonkers on April 19 or at Yankee Stadium the following day, are required to have tickets — all of which have already been given out, according to the Web site of the Archdiocese of New York.

Father O’Connor said that anyone with tickets for the Yankee Stadium address must arrive at the venue at 10 a.m. for the scheduled 2:30 a.m. Mass. He said he has to arrive four hours early for a private mass at the Cathedral of St. Patrick on Saturday.

Upon signing up to become a volunteer to assist in the pope’s visit, one member of the choir at Blessed Sacrament Church, a Wall Street employee, found out that federal agents were looking into his background by calling some of his associates, Father O’Connor said.

“The amount of security precautions they are taking is incredible,” he said.