Local and national security officials on Wednesday night sought to tamp down anxiety in Chicago’s business community about the upcoming NATO and G-8 summits, advising hundreds of downtown workers that public transit will remain open, retailers should not close up shop and - above all - to “calm down.”

“The city can handle it, the federal law enforcement agencies can handle it, and the Chicago Police Department can definitely handle it,” said former Chicago Police Superintendent Terry Hillard, who now runs Hillard Heintze, the private security firm that organized the event. “So I would ask you to calm down, listen to the experts, and let’s not go wild about this.”

The meeting was called by trade groups representing downtown workers and building owners, who say their members have been clamoring for more information about what to expect when hundreds of international leaders - and likely thousands of protesters - descend upon the city for the overlapping summits on May 19-21 at McCormick Place.

Top officials from the Chicago Police Department, the city’s Office of Emergency Management and Communications, the FBI and the U.S. Secret Service said Chicagoans won’t find out exact details on how summit security will affect the city until a couple of weeks before the world meetings. But they urged downtown businesses to carry on as usual during the summits.

“Our expectation is a minimal [level] of disruption to the downtown area, and our expectation is to bring Chicago through this with a sense that we’re a world-class city hosting a world-class event,” Police Superintendent Garry McCarthy said. “That’s an expectation. That’s not a hope.”

Employees will still be able to get to work downtown on public transit, save for temporary hiccups as high-profile motorcades travel to and from the meetings, said Gary Schenkel, who head’s Chicago’s OEMC. And despite some tighter airspace restrictions as world leaders land at O’Hare, there will be a “negligible impact on commercial flights,” he said.

Another priority is making sure tourists can move about freely during a weekend that could see NBA playoffs and a Cubs-White Sox baseball series in Chicago, said Frank Benedetto with the U.S. Secret Service, which is the agency in charge of security plans for the event.

“Business has to be conducted in the Loop, Navy Pier has to operate and the general public has to come and go and do what they do on a weekend in Chicago,” Benedetto said.

While offering few security specifics, Benedetto did reveal that people who work near the summits may need identification to get into the office. And he said some boats docked at Burnham Harbor, near McCormick Place, will have to be temporarily relocated.

Recent news reports have stoked fears among downtown workers about an all-out lockdown of Chicago’s Loop, sharpshooters posted on rooftops and a call by one leftist magazine for 50,000 protesters to flock to the city during the summits.

Audience questions for the panel highlighted how little is still known about security and protesters, just three months before the summits: Would police tear gas seep into the ventilation systems at downtown buildings? Will there be enough cops to quell potential riots in outlying neighborhoods? Can I still    go to church on Sunday?

“Stay vigilant. Stay alert. But the one thing that I told you at first: Calm down,” Hillard said at the end of the meeting. “Calm down. We gonna be okay.”