TOKYO — Toyota acknowledged design problems with the brakes in its prized Prius, adding to the catalog of woes for the Japanese automaker as it reels from massive gas-pedal recalls in the U.S.

Toyota said today it found design problems with the antilock brake system and corrected them for Prius models sold since late January, including those being shipped overseas.

But the company said it was still investigating how to inform customers who had bought them earlier. Nothing was decided on that front for Prius gas-electric hybrids sold outside Japan, according to Toyota.

Complaints about braking problems in the Prius — the world's top-selling hybrid — have been reported in the U.S. and Japan, combining to some 180, and come amid a global recall of nearly 4.5 million vehicles for faulty gas pedals.

Paul Nolasco, a company spokesman, said the time lag for brakes kicking in felt by drivers stem from the two systems in a gas-electric hybrid — the gas-engine and the electric motor.

When the car moves on a bumpy or slippery surface, a driver can feel a pause in the braking when the vehicle switches between the traditional hydraulic brakes and the electronically operated braking system, he said.

The brakes start to work if the driver keeps pushing the pedal, but the driver may momentarily feel they aren't working, he said. Fixing that included a software programming change, he said.

Whether a recall Is in the works for the Prius is still undecided, according to Toyota, but the transport minister urged the company to consider it and is ordering an investigation.