The man tipped to lead U.S. President Barack Obama's recovery plan for the flagging American economy apologized to Congress on Wednesday during his confirmation hearing, saying he was careless in not paying $34,000 US in taxes earlier this decade.

Treasury secretary-designate Tim Geithner called the failure to pay the social security and Medicare taxes "careless mistakes" and unavoidable ones.

The former head of the New York Federal Reserve told the Senate finance committee the failure to pay was "unintentional."

"I should have been more careful," he said.

Earlier, committee chairman Max Baucus said he thought that Geithner had made "disappointing mistakes" but also said he needed to be confirmed so he could get to work on solving the country's financial crisis.

Despite the rough ride, Geithner appears to have wide support from the committee's Democratic and Republican members and is expected to be approved.

Bailout program 'needs serious reform'

Geithner said Obama would be laying out the details of his economic stimulus plan in the next few weeks and vowed the new administration would act with "the strength, speed and care necessary to get our economy back on track."

He also said the Senate's decision last week to permit use of the second $350 billion instalment of a financial industry bailout "will enable us to take the steps necessary to help get credit flowing."

But he added both he and Obama agreed with lawmakers that the program "needs serious reform."

Geithner, 47, served as a Treasury Department official during the Clinton administration, where he played a major role in negotiating assistance packages for South Korea and Brazil.

He has been credited for shaping the dramatic economic response of the Bush administration to the mortgage-led financial crisis, including the landmark $700-bilion bailout package of the country's financial institutions.

With files from the Associated Press