United Nations, Sep 23 - President Barack Obama has called upon world leaders to usher in 'a new era of engagement based on mutual interest and mutual respect' even as he acknowledged that the US has fallen short on many fronts in the past.

Addressing the UN General Assembly Wednesday for the first time as president, Obama defended the actions of his young administration as initial steps toward progress on intractable world problems and asked other leaders too to live up to their responsibilities.

'Make no mistake: this cannot solely be America's endeavour,' Obama said. 'Those who used to chastise America for acting alone in the world cannot now stand by and wait for America to solve the world's problems alone.'

Obama discussed issues of nuclear proliferation, peace and security, climate change and global growth and development and suggested Washington was engaging with the UN in a more complete way than it did during the Bush administration.

But Obama also acknowledged that the US and its world partners over time have failed to confront some of the global problems seriously. 'If we are honest with ourselves, we need to admit that we are not living up to that responsibility,' he said.

'We can be remembered as a generation that chose to drag the arguments of the 20th century into the 21st; that put off hard choices, refused to look ahead, and failed to keep pace because we defined ourselves by what we were against instead of what we were for.