Charlotte officials plan to buttress the city's sizable police force with about 3,400 extra officers during the 2012 Democratic National Convention to help protect top politicians from across the country.

The additions from other agencies will help the Charlotte-Mecklenburg Police Department and the U.S. Secret Service provide security and crowd control for the quadrennial event the week of Sept. 3, says an AP report.

The convention will be held at Time Warner Cable Arena.

But city spokeswoman Kim McMillan said the convention is the most complex because of the security needed, the report says. Besides President Obama and 35,000 other convention participants, tens of thousands more were expected to hit the streets to protest the event.

Officials did not specify where the extra police would come from, but they would have to be sworn officers in North Carolina to arrest anyone.

City police are already monitoring far-left anarchists groups. Members of tea party groups are also planning a big turnout, the report says.

The extra police and other added security for the convention are expected to cost about $50 million, the report says, and the bill will be paid through a federal grant. A similar amount is expected to be spent for the Republican National Convention in Tampa, Fla., the week of Aug. 27.