New York City Mayor Michael Bloomberg on Tuesday made the case for his congestion pricing plan on day two of the C40 Large Cities Climate Summit being held in Midtown Manhattan.

"We'd be the first American city to experiment with congestion pricing -- and going first is always the hardest. But I'm very hopeful of making it a reality," Bloomberg said in his keynote speech at the summit.

The conference, the second of its kind, is being hosted by Bloomberg and former U.S. President Bill Clinton.

Leaders of more than 40 world large cities, along with CEOs from a number of international companies, attended the four-day conference to address the role large cities must play in reversing or reducing the impact of global warming.

"Mayors can't wait for the future," said Bloomberg. "For you to say we are going to do something down the road for 2050, when none of us are going to be alive, is ridiculous."

A panel discussion was held on transport, during which London Mayor Ken Livingstone said his city's traffic dropped some 20 percent after a congestion charge was put in place four years ago.

He said at first the decision was not a popular move, but his popularity soared some 20 percent about a week after the charge was implemented.

Bloomberg was in Albany on Monday trying to get lawmakers to review his plan, which calls for charging drivers eight dollars to get into the busiest parts of Manhattan during rush hour.

London, Stockholm and Singapore are the only cities to have adopted such measures to control traffic.