Toyota Motor has submitted a letter to the U.S. Congress denying there was a fault with the electronics in millions of vehicles it has recalled due to problems with the accelerator, reports said Sunday.

In its letter submitted to the U.S. House Oversight and Government Reform Committee, which is investigating the Toyota recalls, the automaker said it "is convinced that there is no problem" with the electronics in its vehicles, the Japanese dailies Yomiuri and Nikkei reported, without disclosing sources.

Toyota also referred to its plans to expand the number of vehicles equipped with computerised brake override systems designed to prevent unintended acceleration, stressing its drive to improve safety measures on its vehicles, the Yomiuri said.

The reports came as embattled Toyota president Akio Toyoda was reportedly prepared to testify at U.S. congressional hearings if formally asked to do so, with the automaker facing intense pressure in the United States over the rash of recalls.

The Japanese giant has recalled millions of vehicles worldwide in past months due to problems linked to accelerator and brake functions, sullying the company's safety reputation, AFP reported.

A separate report by the Wall Street Journal said that Toyota commissioned a study into the electronics in its vehicles that supported the carmaker's assertion that there was no evidence of problems in the electronics.

"Exponent has so far been unable to induce, through electrical disturbances to the system, either unintended acceleration or behaviour that might be a precursor to such an event, despite concerted efforts toward this goal," concludes the study being carried out by engineering research firm Exponent, the U.S. business daily said online.

The preliminary study has been shared with U.S. lawmakers planning hearings on Toyota's safety record, it said.

Officials of Toyota were not immediately available to comment on the reports.