Japan's Toshiba Corp is in discussions to buy out Shaw Group's 20 percent stake in nuclear power plant company Westinghouse Electric Co, the Wall Street Journal reported, in a deal that could erase any U.S. ownership of Westinghouse.

A deal could be announced as early as Tuesday, although the discussions are still ongoing and could fall apart, the paper said, citing people familiar with the matter.

Shares of Toshiba fell as much as 5.4 percent in early trade on Tuesday.

Officials at Toshiba and Westinghouse were not immediately available for comment. Shaw declined to comment.

Westinghouse is already majority owned by Toshiba -- a maker of flash memory chips, laptops, nuclear reactors and rice cookers -- and Shaw Group.

Shaw partnered with Toshiba and Japanese engineering firm IHI Corp to buy Westinghouse from British Nuclear Fuels PLC for $5.4 billion five years ago, the paper said. Toshiba bought 77 percent, Shaw purchased 20 percent, and IHI took 3 percent.