Access to Pope Francis during his visit to New York City will be so strict officials Monday had an important reminder for anyone with credentials or tickets for his visit to Central Park, the Madison Square Garden Mass and elsewhere: Bring valid ID.

Failure to have the right identification will lead to people being turned away, officials said at a briefing for reporters Monday at NYPD headquarters that included Mayor Bill de Blasio, NYPD Commissioner William Bratton and members of the Secret Service.

Officials outlined the size of the security operation to protect the pope and the 170 world leaders in town for the UN General Assembly session that begins Tuesday.

While security will be tight, officials acknowledged that Francis' desire to be close to the public creates the possibility of unscripted detours from his tight schedule that includes a visit to a Bronx parochial school and motorcade through Central Park.

"We are trying to the best of our ability to meet our needs and the desires and wishes of the pope," Bratton said.

De Blasio said security "will involve tools and measures you can see and many you can't see."

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Later, de Blasio walked among an array of vehicles from the police emergency service unit as well as a strategic response group containing tactical police gear.

The vehicles contain chemical, biological and radiological detectors for deployment across the city. As many as 5,000 cops are expected to cover the papal visit and UN meetings.

"It is something we use everyday, even more when the pope is coming, of course," said Chief Harry Wedin, head of the NYPD's special operations division. "Any rescue equipment you could possibly think of is on these trucks."

The trucks will be deployed at all venues Pope Francis visits, said Deputy Chief Vincent Giordano, head of the emergency services unit.

Earlier in the day, city, police and federal officials held a tabletop exercise at the NYPD's joint operations center to run through emergency scenarios to protect the pope and world leaders. A pool reporter was allowed to attend for a brief period.

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One scenario involved two active shooters near hotels, a building collapse in Brooklyn and a power outage. None of the hypotheticals involved the pope. Deputy NYPD commissioner John Miller said that at one point a loudspeaker in the center stated that NASA had reported an asteroid headed toward the city. For about two seconds there was silence. The tension broke when everyone was told it was a joke, Miller said.

In another lighter moment, Bratton said the pope would need to pay his fare if he took a subway ride.

"There are strong laws against fare evasion here," Bratton said with a chuckle.