Toyota Motor Corp. is set to announce a recall this week over brake problems with its 2010 Prius hybrid both in the United States and Japan, affecting more than 270,000 vehicles, sources said Monday.

With criticism already mounting about its response to a recent spate of quality issues, the world's biggest automaker decided on the mandatory recall, rather than voluntary repairs, to address growing complaints over its best-selling hybrid, the sources said.

The recall would affect about 100,000 cars in the United States and around 170,000 in Japan. The model was released last May in Japan and in June in the United States.

Japanese dealers have already been notified of the recall and will begin the repairs once Toyota reports it to the Land, Infrastructure, Transport and Tourism Ministry, which is expected to happen early this week.

Because dealers cannot notify their customers about a recall until the official procedure with the government is completed, many are currently scrambling to deal with a growing number of inquiries from confused drivers.

"If there is a problem, I wish they would admit it quickly and disclose specific measures (to address it)," a dealer in Hiroshima Prefecture said.

Toyota officials earlier emphasized that complaints over the Prius brakes temporarily not working properly do not involve serious defects and the firm has sought to fix them on a voluntary basis under what they dub a "service campaign."

When the recall is carried out, owners can bring their Prius to a nearby dealer where the problems can be fixed by improving the software for the antilock brake system.

The software for the repair has already arrived at some dealers.

"Once the recall is announced, we are prepared to be open on our regular holidays to respond (to our customers)," a manager at a dealership in Fukushima Prefecture said.