In one example, the report cited figures from western New York state, where 40 per cent of black, Hispanic and ethnically-mixed households earned less than $15,000 in 1999, as compared to 15 per cent of white households.
Beijing 'most equal'
The most balanced city, both in Asia and in the world, is Beijing, the capital of China, whereas the least egalitarian in Asia is Hong Kong, the Chinese-administered former British colony, the report found.
The world's most equal cities are located, on average, in western Europe, it said.
Denmark, Finland, the Netherlands and Slovenia were among those with the lowest levels of inequality, it said.
In Latin America, Brazilian cities "have the greatest disparities in income distribution in the world," the UN repot said.
Brazil is struggling to control rising unemployment and declining wages.
Cities in sub-Saharan Africa have the world's highest levels of urban poverty, with more than half of city residents living below the poverty line.
The report also said cities in South Africa and Namibia continue to have extremely high levels of income inequality, despite the end of apartheid early in the 1990s.