The White House is looking for ways to help the city of Detroit after the city filed for bankruptcy protection on Thursday, but Vice President Joe Biden said it was unclear what the administration could do.

"Can we help Detroit?" Biden said on Friday in a response to a question from a reporter. "We don't know."

Detroit, a former manufacturing powerhouse and cradle of the U.S. automotive industry, filed for Chapter 9 bankruptcy protection on Thursday, making it the largest municipal bankruptcy in U.S. history.

White House spokesman Jay Carey dismissed a question of whether there could be a government bailout for the city, but shed little light on other "policy options" under consideration.

"I would point you to what we have said and what leaders in Michigan and Detroit have said, which is that on the matter of their insolvency, that's something for the city and the creditors to resolve," he told reporters.

Top White House officials talking to the city and state have included Valerie Jarrett, Obama's senior adviser, Gene Sperling, the head of the National Economic Council, and Shaun Donovan, secretary of Housing and Urban Development, Carney said.

President Barack Obama made saving the automotive industry in Detroit a priority of his first term.

"We're concerned, obviously, about the citizens of Detroit and of the state, and continuing to assist Detroit in moving forward," Carney said.