President Barack Obama warned the nation's big city mayors Friday that he's expecting the stimulus money to be spent on deserving projects -- and not wasted on political pork.

He called for ''unprecedented responsibility and accountability'' on the spending.

''Without waste, without inefficiency, without fraud,'' he said.

''We cannot tolerate business as usual,'' he added, warning that he'd ''call out'' wasteful projects.

Obama gave a shout out to Chicago Mayor Richard Daley and joked that he's ''surprised he's still talking to me'' -- since Obama named his hometown city's school chief, Arne Duncan, as education secretary.

Vice President Joe Biden delivered the welcoming remarks, joking that 'in a long life in politics,'` he never ran for mayor ``because it's too hard.''

''They have your phone number, they know where you live,'' he told the mayors to laughter. Biden told the mayors that the stimulus package -- which most of them backed -- includes ''unprecedented investment'' in the nation's cities.

''The world's watching to see how this works and we need your help in making it work,'' he told the mayors.