Washington - US President George W Bush Friday thanked the US Congress for passage of the emergency rescue plan for the country's finance system but warned that economic improvement won't happen "overnight."

"It will take some time for this legislation to have its full impact on our economy," Bush told reporters at the White House less than an hour after the measure cleared its final hurdle in the House of Representatives.

Bush said he would sign the legislation into law.

Bush, an ardent Republican advocate of free markets, over the past year has insisted the markets would solve the growing credit crunch caused by mortgage assets gone sour, and his philosophy came through in his remarks.

"I believe government intervention should occur only when necessary," he said. "In this situation, action is clearly necessary."

The 700-billion-dollar rescue plan calls for a complicated and unprecedented purchase by the government of mortgage securities and other toxic securities. Democrats charge the problem illustrates the lax regulation of Bush's eight years in the White House.

Secretary of the Treasury Henry Paulson has said the government would start buying up bad securities at the lowest prices in a reverse-auction process. Both struggling and healthy financial firms will be encouraged to get the assets off their books so they can start lending money again to businesses and consumers.

Bush said the Treasury Department would use careful analysis and deliberation, but it "cannot be accomplished overnight."

After the House voted 263 to 171 in bipartisan support for the emergency measure, Speaker of the House Nancy Pelosi announced a new era of regulation to corral the "chaos" on Wall Street that created the crisis.

Bush said that Congress had come together on the legislation to act "boldly to help prevent the crisis on Wall Street from becoming a crisis in communities across our country."

"We have shown the world that the United States of America will stabilize our financial markets and maintain a leading role in the global economy." (dpa)