Mr Johnson has promised New York-style policing
London mayor Boris Johnson has hailed a "new era of co-operation" with New York after a new partnership was announced between the two world cities.
The new Tory mayor met his counterpart Michael Bloomberg at City Hall.
The exchange programme is designed to share best practices in government innovation, London's mayor said.
Outside City Hall there were protests as the BNP's Richard Barnbrook entered to sit on the first meeting of the newly-elected London Assembly.
The Innovation Exchange Programme will look at transparency and accountability, efficiency, transport, policing, education and skills and environmental policy.
As well as a formal exchange of ideas, it will also include personnel exchanges.
Mr Johnson said: "Mayor Bloomberg has shown inspirational leadership and I am delighted we are establishing this new era of co-operation.
The BNP's Richard Barnbrook was confronted by protesters
"I have been particularly impressed by Mayor Bloomberg's achievements in expanding educational opportunities, providing more accountable government and delivering taxpayer value."
Mr Bloomberg said: "No matter where in the world you are Mayor, the goals are always the same - clean streets, strong schools, thriving businesses and, most important, safe neighbourhoods.
"Mayor Johnson and I had a productive discussion about these and other issues this morning, and I look forward to working with him on the challenges we share."
As the two mayors were meeting there were tense exchanges outside City Hall as Mr Barnbrook entered the building to sit on his first London Assembly meeting.
He was confronted by a 17-strong group of Socialist Party supporters.