Toyota memo shows staff trumpeting savings of $100 million by halting U.S. safety investigation in 2007

Toyota's President Akio Toyoda testifies before U.S. Congress this week in an attempt to contain a safety crisis that threatens the company's global reputation and continued success.

The newly emerged document will add more weight to the high-stakes debate about whether Toyota missed or ignored complaints about sudden acceleration in its cars and whether U.S. safety regulators were tough enough.

The Japanese automaker has recently recalled over 8.5 million vehicles globally.

Toyota on Sunday insisted that it was thoroughly reviewing all its operations. "Our first priority is the safety of our customers and to conclude otherwise on the basis of one internal presentation is wrong," the company said.

However, the U.S. Department of Transportation said the document highlighted Toyota's slow response to the safety problems.

"Unfortunately, this document is very telling," said spokeswoman Olivia Alair in a statement.