The most significant remarks, nevertheless, came from the host President Obama.

'Power is no longer a zero sum game. No nation can or should try to dominate another nation. No world order that elevates one nation or group of people over another will succeed,' said the US president.

According to diplomats, the G20 leaders were also expected to issue a statement at the end of the summit Friday committing themselves to a framework of sustainable and balanced growth.

Their first interaction is scheduled at the Phipps Conservatory and Botanical Gardens, where President Obama will host a welcome reception, following which they will meet at the sprawling David Lawrence Convention Centre Friday.

The city, meanwhile was geared to tackle any protest that turns ugly, with the federal government expected to spend some $10 million on security arrangements with another $4 million by the state of Pennsylvania.

The green banners put up in the city read: 'Pittsburgh welcomes the world', even as police was patrolling the areas near the venue on foot, helicopters and even bicycles.