The Occupy Wall Street protesters may not be able to camp out in a downtown park indefinitely, Mayor Michael R. Bloomberg warned on Friday morning.

“People have a right to protest but we also have to make sure that people who don’t want to protest can go down the streets unmolested,” the mayor. “We have to make sure that while you have a right to say what you want to say, people who want to say something very different have a right to say that, as well. That’s what’s great about this country.”

Asked by the radio host John Gambling if the protesters would be allowed to stay as long as they wanted in Zuccotti Park, a public-private park, Mr. Bloomberg said, “We’ll see.”

“You’re worried about sanitation, and you’re worried about lots of different — there’s lots of laws on the books of what you can do in parks and that sort of thing,” he said on the weekly radio show that he appears on with Mr. Gambling.

Mr. Bloomberg also suggested that the protesters were misguided, emphasizing that financial institutions employ large numbers of New Yorkers — many of them not wealthy executives.

“The protesters are protesting against people who make forty, fifty thousand dollars a year and are struggling to make ends’ meet — that’s the bottom line,” the mayor said, adding: “People in this day and age need support for their employers.”

Mr. Bloomberg, who began his career on Wall Street and made his considerable fortune in a media company that caters largely to financial institutions, has been a prominent defender of banks as they face criticism for their risky practices in the run-up to the financial crisis. On Friday, he argued, as he has done many times recently, that attacking banks is counterproductive when trying to help the economy.

“If the banks don’t go out and make loans, we will not come out of our economic problems, we will not have jobs,” he said, “and so anything we can do to responsibly help the banks do that, encourage them to do that is what we need.”

He was not asked, and did not comment, on the growing controversy over the tactics employed by the police, including the use of pepper spray, to control the protesters.

The discussion of the Wall Street demonstrations prompted Mr. Bloomberg to recall an earlier era of protest, the mass marches against the Vietnam War.

“I remember in the Vietnam War there were enormous protests on Wall Street,” said Mr. Bloomberg, who was working for Salomon Brothers at the time. “I’ve always thought one of the sad things is when the Vietnam vets came back we didn’t treat them the way they deserve to be treated.”

Mr. Bloomberg did not serve in Vietnam, having been classified as 1Y — draftable only in a national emergency — due to having flat feet.

“Whether you support a war or not,” he said, “our vets deserve the respect and the help when they get back.”