WASHINGTON – Toyota Motor Corp. apologized for letting safety standards slip during a period of fast growth and vowed to respond more quickly to consumer complaints as two days of congressional hearings crucial to the automaker's reputation began on Tuesday, Reuters reported.

President Akio Toyoda said he was "deeply sorry" for accidents caused by safety problems with Toyota vehicles and detailed a set of reforms that would shift control of recall decisions away from the automaker's Japanese headquarters.

The world's largest automaker is seeking to repair damage over unintended acceleration and braking problems that have led to the recall of more than 8.5 million vehicles globally.

"We pursued growth over the speed at which we were able to develop our people and our organization, and we should sincerely be mindful of that," Toyoda said in written testimony for a hearing scheduled for Wednesday.

Toyota's recent safety problems revolve around sticky accelerators, accelerators that can be pinned down by loose floor mats and a braking glitch affecting its hybrid models.

But many lawmakers, some Toyota owners and safety experts fear Toyota's current recalls do not cover all complaints of runaway acceleration and also want reforms at the National Highway Traffic Safety Administration.

Toyota's top-ranking U.S. executive, Jim Lentz, arrived for Tuesday's hearing in a silver 2010 Toyota Highlander SUV, one of the vehicles subject to the sticky accelerator recall.

"We now understand that we must think differently when investigating complaints and communicate faster, better and more effectively with our customers and our regulators," said Lentz, Toyota's U.S. sales chief.

Under questioning, Lentz agreed that 70 percent of complaints about unintended acceleration remained unexplained. "That is probably fair to say," he said. "There are many factors that lead to it."

U.S. Transportation Secretary Ray LaHood said he would hold Toyoda to his assurance that the carmaker is working to address all safety issues.