WASHINGTON — Treasury Secretary Henry Paulson says the bold approach needed to take troubled assets off the books of financial organizations will be expensive but doing nothing would cost far more.

Mr. Paulson said today that he planned to work through the weekend with congressional leaders to reach agreement on a plan that would address the root problems of the financial crisis gripping the country.

Speaking to reporters at the Treasury Department, Mr. Paulson said that the new troubled-asset relief program that he wants Congress to enact must be large enough to have the necessary impact while protecting taxpayers as much as possible.

“I am convinced that this bold approach will cost American families far less than the alternative — a continuing series of financial institution failures and frozen credit markets unable to fund economic expansion,” Mr. Paulson said in a prepared statement.

“The financial security of all Americans … depends on our ability to restore our financial institutions to a sound footing,” Mr. Paulson said.