WASHINGTON - On the defensive over a half-billion-dollar loan to a now-bankrupt solar company, the White House on Friday ordered an independent review of similar loans made by the Energy Department, its latest response to rising criticism over Solyndra Inc.

The announcement came as House Republicans prepared for a possible vote next week to subpoena White House documents related to the defunct California company.

White House officials said the review would assess the health of more than two dozen other renewable energy loans and loan guarantees made by the Energy Department program that supported Solyndra. Congressional Republicans have been investigating the company's bankruptcy amid embarrassing revelations that federal officials were warned it had problems but nonetheless continued to support it, and sent President Barack Obama to visit the company and praise it publicly.

"Today we are directing that an independent analysis be conducted of the current state of the Department of Energy loan portfolio, focusing on future loan monitoring and management," White House chief of staff Bill Daley said. "While we continue to take steps to make sure the United States remains competitive in the 21st century energy economy, we must also ensure that we are strong stewards of taxpayer dollars."

Daley said the review would be conducted by former Treasury official Herb Allison, who oversaw the Troubled Asset Relief Program, part of the 2008 Wall Street bailout. The review would not look at the Solyndra case but would evaluate other loans worth tens of billions of dollars and recommend steps to stabilize them if they appear to have problems like the loan to Solyndra.

Energy Secretary Steven Chu said in a statement that he welcomed the White House review.

House Republicans are preparing to ramp up their investigation of Solyndra, which is proving a political headache for the White House and providing fodder for opponents of Obama's renewable energy agenda.

The White House has already refused a request by the Republican-controlled House Energy and Commerce Committee for all its internal communications about Solyndra, which closed its doors and filed for bankruptcy protection earlier this year, costing 1,100 jobs.