The U.S. government is pressing Japanese auto giant Toyota about the automaker's spate of recalls in the United States as Transportation Secretary Ray LaHood said on Wednesday that he plans to speak with Toyota President Akio Toyoda and expressed his concerns at the Congress.

LaHood said he will call Toyoda in the coming days to make sure the Japanese automaker is aware of the U.S. government's concerns about safety issues with Toyota vehicles.

He also said that the National Highway Traffic Safety Administration will conduct an investigation into electronic throttle control systems and potential electromagnetic interference in the nation's fleet of vehicles.

In a statement, HaHood said that the government "will continue to hold Toyota's feet to the fire to make sure that they are doing everything they have promised to make their vehicles safe."

Besides, the agency was studying the possibility of civil penalties on Toyota for safety violations, which could mean fines of millions of dollars.

LaHood told a congressional panel that owners of millions of Toyota vehicles affected by the defect which causes sudden, unintended acceleration should "stop driving" them.

On Tuesday, LaHood said Toyota's recall of millions of vehicles with defective pedals that can get stuck and cause unwanted acceleration came only after pressure from the US government.

But Toyota said it had made the recall voluntarily.

Analysts said that Toyota, which overtook General Motors in 2008 as the top-selling automaker, is losing its reputation as one of the safest and most reliable vehicles.

The company is recalling almost eight million vehicles worldwide -- roughly equivalent to its entire 2009 global sales -- due to problems with accelerator pedals that could cause the car to speed up unintentionally.

Industry data showed that sales by U.S. domestic automaker brands General Motors and Ford increased in recent months when Toyota fell.