WASHINGTON (AFP) - US Treasury Secretary Timothy Geithner said Sunday that any recovery of the world's largest economy from prolonged recession has to be sustainable and not based on an "artificial boom."

Speaking ahead of a London G20 summit where the global economic crisis will take center stage, he said most private economists believed the US economy would hit "a more durable bottom" in the second half of 2009 to set the stage for resumption of growth.

"We want to have a stronger, more sustainable recovery, not a recovery based on an artificial boom that is not going to be sustainable," he said in an interview with the NBC broadcast network.

"We need to end this pattern of having booms and busts. That has to change," said Geithner, who is President Barack Obama's pointman to contain the crisis, stemming from a financial meltdown caused by trillions of dollars in securities tied to high-risk home loans.

The US economy fell into recession in December 2007, with growth contracting 6.3 percent in the last quarter of 2008 and unemployment soaring to 8.1 percent.

Geithner, in a separate interview with the ABC broadcast network, cautioned that economic recovery would come slowly although there were various indicators showing the recession could be easing.

Latest government data showed positive signs for orders for US-made manufactured goods, new home sales and mortgage refinances.

"They came in above expectations. But it's very important for people to understand that, you know, it took us a long time to get into this mess," Geithner said.

"It's going to take us a while to get out of this. Progress is not going to be even. It's not going to be steady," said Geithner, who will accompany Obama to the Group of 20 summit of developed and developing economies on April 2.

The summit is aimed at coordinating global efforts to fight the economic downturn and preventing similar crises, including reforming the key financial sector.

Group of 20 leaders predict that the world economy will start to grow again by the end of 2010 in a draft communique for the summit, the Financial Times reported Sunday.

The 24-point draft reiterates pledges to avoid protectionism but is sketchy about a global approach to a fiscal stimulus package.

Geithner also asked Americans to brace for more bleeding in the financial system before it could resume its critical role of economic growth driver.

"There's no doubt there's more losses ahead for the financial system, but we've had a lot of adjustment already. One of the things about the American economy is, change happens here with brutal force, much more quickly than it happens around the world."

He said that the Treasury still had US$135 billion dollars from a US$700 billion fund approved by Congress to shore up the troubled financial sector.

The estimate included money that could be returned by banks that had borrowed but did not need to tide them through the turmoil, he said.

"That's a reasonably conservative estimate and gives us, this is very important, substantial resources to move ahead with this broad-based initiative to get the financial system back in the business of providing credit," Geithner said.

Congress approved in October last year a US$700 billion program to fix the critical financial sector, including government involvement with the private sector to clean up bank balance sheets of "toxic" assets.

The troubled assets mostly involved home mortgage securities that soured.

On the prospect of going to Congress again to seek additional funds to beef up the financial sector, he said, "We'll cross that bridge when we come to it. "If we come to that point we'll go to the Congress and give us the strongest case possible and help them understand why this will be cheaper over the long run for us to move aggressively."

Geithner also said that crisis would help end financial and other "excesses" that had overwhelmed the US economy.

"I think the adjustment to the period of excess is necessary. You never wanted to have a crisis to remind people of the importance of living within your means, not borrowing too much, or why regulation is important," he said.

"When we get through this, people are going to care less about what they make, more about what they do with what they achieve...and that will help make this country stronger."