The Japanese conglomerate's board approved the Chapter 11 filing in a US court in New York, a step that temporarily shelters struggling firms as they try to restructure their affairs and debts.

Westinghouse technology is at the core of about half of the world's nuclear reactors.

"Westinghouse Electric.... and certain of its subsidiaries and affiliates, today filed voluntary petitions under Chapter 11 of the US Bankruptcy Code," the US firm said in a statement.

"The company is seeking to undertake a strategic restructuring as a result of certain financial and construction challenges," said Westinghouse, which is based outside Pittsburgh, Pennsylvania.

Toshiba has previously warned it was facing a writedown topping 700 billion yen ($6.3 billion) at Westinghouse.

The Japanese conglomerate's shares have lost more than half their market value since late December when Toshiba warned of a flood of red ink at Westinghouse and said it was investigating whistleblower claims of possible accounting fraud by senior executives at the division.