US Energy Secretary Steven Chu will testify to a key congressional committee November 17 about a half billion-dollar loan to now bankrupt solar panel firm Solyndra, the panel announced late Thursday.

President Barack Obama's Republican foes have been hunting for evidence that politics at the White House improperly shaped the US Energy Department's decision to provide Solyndra with a $535-million loan guarantee.

The White House has denied acting inappropriately.

The chairman of the House Energy and Commerce Subcommittee on Oversight and Investigations, Republican Cliff Stearns, announced that Chu would testify before his panel and signalled that the official would face a grilling.

"We hope he will finally provide answers about why DOE consciously ignored the direct warnings from their own experts that Solyndra was doomed to fail, and granted the loan to Solyndra," Stearns said in a statement.

Stearns also accused Chu and his department of illegally restructuring Solyndra's loan at a time when the failed firm "was fresh out of cash."

"Dr Chu's testimony is an important piece of the overall Solyndra puzzle as we seek answers on why taxpayers are now on the hook for a half billion dollars," the lawmaker added.

Critics of the administration say that the firm, once hailed as a shining example of Obama's push to create green jobs in a new energy economy, was instead an symbol of unwise federal handouts.

California-based Solyndra has now filed for bankruptcy, closed its doors and laid off 1,000 workers, leaving taxpayers on the hook for the loan.