WASHINGTON - President Barack Obama sternly warned Wall Street on Monday against returning to the sort of reckless and unchecked behaviour that threatened America with a second Great Depression.

Even as he noted the U.S. economy and financial system were pulling out of a downward spiral, Obama warned financial titans on the first anniversary of the Lehman Brothers collapse that they could not count on any more bailouts.

He credited his administration and the $787 billion stimulus package rammed through Congress in the first days of his taking office for pulling the country back from the brink.

"We can be confident that the storms of the past two years are beginning to break," he said.

And even as the economy begins a "return to normalcy," Obama said, "normalcy cannot lead to complacency."

Nevertheless, Obama said, "Instead of learning the lessons of Lehman and the crisis from which we are still recovering, they are choosing to ignore them."

His tough message warned the financial community to "hear my words: We will not go back to the days of reckless behaviour and unchecked excess at the heart of this crisis, where too many were motivated only by the appetite for quick kills and bloated bonuses."

Obama spoke at Federal Hall in the heart of Wall Street before an audience that included members of the financial community, legislators, and top administration officials.

In marking his determination to prevent a repeat of the crisis that nearly brought down the global financial system last fall, Obama said he was attacking the problem on several broad fronts, including new rules to protect consumers and a new Consumer Financial Protection Agency to enforce those rules and closure of regulator loopholes and overlap that "were at the heart of the crisis" because it left key officials without "the authority to take action."

At the Pittsburgh Group of 20 economic meeting later this month, Obama said the U.S. will focus on ways "to spur global demand but also to address the underlying problems that caused such a deep and lasting global recession."

Obama and others seeking ways to better monitor the financial system and to police the products banks sell to consumers have been opposed by lobbyists, legislators and turf-protecting regulators. Mergers and sales of banks have consolidated lending power in even few hands. And those large firms still bet far more than the capital they have on hand.

Yet regulations have not moved. Much of the legislative motivation in Washington has been consumed by the contentious debate over changes to the health-care system. Government intervention into private automakers such as General Motors have left lawmakers skittish to move further into corporate board rooms. And it's not as if another collapse is obviously imminent.

Five of the biggest banks - Goldman Sachs, JPMorgan Chase, Wells Fargo, Citigroup and Bank of America - posted second-quarter profits totalling $13 billion. That's more than double what they made in the second quarter of 2008 and nearly two-thirds as much as the $20.7 billion they earned in the second quarter of 2007 - when the economy was considered strong.

The failure of Lehman Brothers - the biggest bankruptcy in U.S. history - and the panicky sales of Bear Stearns to JPMorgan Chase and Merrill Lynch to Bank of America transformed Wall Street and gave fewer competitors increased market power.

As of June 30, three banks - JPMorgan Chase, Wells Fargo and Bank of America - held $2.3 trillion in domestic deposits, or $3 out of every $10 in deposit in the United States. Three years ago those three institutions held about 20 per cent of the industry total.

Obama has sought tougher capital requirements for banks, arguing that banks' buying of exotic financial products without keeping enough cash on reserve was a key cause of the crisis. Treasury Secretary Timothy Geithner has urged the G20 countries to agree on new capital levels by the end of 2010 and put them in place two years later.

The administration also has proposed increased transparency of markets in which banks trade the most complex - and potentially risky - financial products. Obama's broad plan also would give the Fed new oversight powers and impose conditions designed to discourage companies from getting too big.