WASHINGTON (AFP) - US Treasury Secretary Timothy Geithner said Sunday that US$135 billion (S$203 billion) remained from a US$700 billion (S$1.06 trillion) fund approved by Congress to shore up the financial sector reeling from crisis.

He said it was crucial for President Barack Obama's administration to have substantial resources to implement various steps to rehabilitate banks and other financial institutions bruised by the crisis stemming from a home mortgage meltdown.

"In terms of if you look at what's not committed yet, it's roughly US$135 billion," he said in an interview with the ABC network.

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.

Geithner said that the government would use the funds to "quickly, as carefully as we can," to ease credit flows so that the financial system could resume its role in fueling economic growth.

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 whether we need additional resources.

"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."