By Nobuhiro Kubo and Bernie Woodall

TOKYO/DETROIT (Reuters) - Toyota Motor Corp is recalling nearly half a million of its flagship Prius and other hybrid cars for braking problems, a third major recall since September and a further blow to the reputation of the world's largest automaker.

Toyota is already under fire for two other recalls covering more than 8 million vehicles worldwide due to problems with slipping floormats and sticky accelerator pedals.

It is also facing a potential rush of litigation for crashes linked to unintended acceleration blamed for 19 deaths and numerous injuries in the United States over the past decade.

Criticised by U.S. safety authorities and members of the Obama administration for moving too slowly on those recalls, Toyota said President Akio Toyoda and Executive Vice President Shinichi Sasaki, in charge of quality, would hold a media briefing at 3:30 p.m. (0630 GMT) in Tokyo regarding the recall.

Documents from Toyota and seen by Reuters showed it was recalling a total of 436,000 units of its 2010 Prius, new Sai and Lexus HS250h hybrids globally, including 223,000 in Japan and 150,000 in North America.

The new Prius is sold in some 60 countries, with cumulative sales of almost 350,000 units.

Toyoda said the company founded by his grandfather would work more closely with U.S. regulators.

"I have spoken with U.S. Transportation Secretary Ray LaHood and given him my personal assurance that lines of communications with safety agencies and regulators will be kept open, that we will communicate more frequently and that we will be more vigilant in responding to those officials on all matters," Toyoda wrote in an op-ed in the Washington Post.