Andrew Clark in New York
guardian.co.uk, Sunday 20 September 2009 23.37 BST
The UN roadshow moves to Pittsburgh on Thursday and Friday, where Obama will face delicate negotiations over the global economy, bankers' pay and climate change.
Top of the agenda will be the global economic slowdown. Obama has described the meeting as an opportunity for a "check-up" on countries' initiatives to counter the recession. Along with Gordon Brown, he is keen for progress on a blueprint for international regulation of the financial markets.
But the US faces a confrontation with other European Union countries over calls to restrict multimillion-pound bonuses in the financial industry. Some European leaders want a cap on bankers' pay, and the French president, Nicolas Sarkozy, has threatened to walk out of the summit unless the US moves on the issue. The White House, deeply reluctant to alienate Wall Street, favours far more modest measures to discourage pay deals viewed as encouraging excessive risk-taking.
Emphasising his environmental credentials, Obama has been tipped to use his position as the G20 host to call on member countries to end all subsidies for electricity generated by fossil fuels.
Anti-war, environmental and anti-poverty groups plan to demonstrate in Pittsburgh, with one group marching from a working-class suburb in a "people's uprising". Some 4,000 police reinforcements have been drafted. The city was chosen as the venue to showcase its strength in shifting from heavy manufacturing to production of hi-tech and green goods.