As world leaders and diplomats from around the world converge on Manhattan this week for the United Nations General Assembly, New Yorkers and drivers once again brace for traffic congestion and street closures that come with the annual gathering.

While heads of state discuss and debate the world’s problems, outside the East Side complex the talk will be more humdrum — gridlock.

“This is the worst traffic jam for midtown Manhattan,” said Samuel Schwartz, a former city transportation commissioner and a traffic maven. “There is not a week that’s worse than this coming week.”

The NYPD, which announced street closures beginning late Sunday, will provide security for up to 140 motorcades, with as many as 30 units protecting officials, according to a law-enforcement source familiar with the preparations.

The department’s Strategic Response Group and Critical Response Command officers will be heavily involved in security for the UN, the high-ranking official said.

NYPD Lt. Paul Ng said Friday that the agency does not generally discuss security preparations.

As world leaders start arriving, the number of motorcades will grow, which in turn will lead to more traffic congestion.

Last year, the security and traffic plans had to take into account the presence of both President Barack Obama and Pope Francis, who addressed the General Assembly before going to Philadelphia for the World Meeting of Families. This year, the pontiff is not a factor.

However, Obama, who is scheduled to arrive Sunday evening, plans to be in the city through Wednesday afternoon. During those days, the president will hopscotch around town as he attends various functions, including fundraisers and a visit to the UN.

When his motorcade — which consists of about 35 vehicles, including an ambulance, counter-assault team and the Secret Service — is on the move, traffic likely will not be.

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“Walk, bike, take underground public transportation,” Schwartz said. “Forget about taking the buses — crosstown or on the East Side.”

For those who must drive, stick to the West Side, Schwartz said. Don’t drive on First Avenue or Second Avenue, and avoid the FDR Drive.

“The FDR is the way the president’s motorcade drives north and south,” he said. “It gets shut down when he goes north-south.”

In years past, Obama laid his head at the Waldorf Astoria at the end of a night out in New York City — until last year, when the luxury hotel was bought by Anbang Insurance Group of China.

This week, the president is staying at Lotte New York Palace on Madison Avenue and 50th Street, which will shift the gridlock a bit farther to the middle of the island.

The president’s hotel choice will affect truck traffic the most, Schwartz said. Truck drivers are not allowed to drive on Park Avenue or on Fifth Avenue at all below 125th Street, and losing access to a section of Madison Avenue this week will force truck traffic elsewhere.

“When you lose Madison Avenue, you’re losing one of the key northbound lanes,” he said.

The other road in midtown Manhattan that he suggests avoiding is Fifth Avenue, the shopping mecca packed with high-end shops such as Henri Bendel and Tiffany.

“When heads of state come to New York City, they love to shop. Fifth Avenue often becomes motorcade alley,” Schwartz said. “When I was traffic commissioner, one of my agents ticketed Indira Gandhi’s motorcade.”

With Anthony M. DeStefano