US Transportation Secretary Ray LaHood warned Japanese auto giant Toyota on Monday that the US government "will not sleep" until it is sure the carmaker has made improvements in safety.
During a visit to Toyota's headquarters, LaHood told a press conference that he and Toyota chief Akio Toyoda met for "tough, respectful and serious discussions" about Toyota's commitment to safety.
The world's biggest automaker has seen its reputation battered after recalling around 10 million vehicles worldwide, mostly for problems with sudden acceleration which have been blamed for 58 deaths in the United States.
LaHood's invitation to the auto giant's headquarters follows Toyoda's trip to the United States in February when he tearfully apologised for safety woes following a tense appearance at a congressional hearing into the problems.
Toyoda pledged to overhaul quality control measures, including creating a new US safety post, and requiring executives to do test-drives. Toyota has also pledged to speed up the recall process and improve quality control.
While Toyota has made "very encouraging steps," LaHood warned that the US government "will watch very carefully for improvements in safety."
In April, the company agreed to pay a 16.4-million-dollar fine, the largest for an automaker in the United States, for hiding for at least four months the accelerator pedal defects.
"The proof is in the pudding, and Mr Toyoda understands what that means," said LaHood. "It's fine to have these measures in place but they need to be carried out. We will not sleep until we are sure that all Toyota vehicles are safe for American drivers."