WASHINGTON - General Motors should promptly warn consumers not to drive GM cars recalled because of faulty ignition switches that can unexpectedly turn off engines and air bags as the vehicles are running, U.S. Senator Richard Blumenthal said on Thursday.

Blumenthal, a Democrat from Connecticut who serves on a Senate panel that has scheduled a GM oversight hearing on Wednesday, said in a letter to GM Chief Executive Officer Mary Barra:

"I urge you to issue a stronger warning to drivers of recalled vehicles of the acknowledged risk they are facing, including a warning not to drive recalled cars. This warning should be issued as soon as possible - in advance of your testimony before the Subcommittee."

GM has said that the cars are safe to drive if there is only a key inserted into the ignition, with no other keys or fobs attached that could affect the operation of the ignition switch.

Barra, in a video to customers posted on YouTube, said, "GM engineers have done extensive analysis to make sure if you only have the key, or the key on only the ring, that the vehicle is safe to drive."

Blumenthal, along with fellow Democratic Senator Edward Markey of Massachusetts, has introduced legislation designed to improve the automobile industry's reporting of safety problems.

It would require manufacturers to provide more information about fatal accidents and would give the public better access to such reports.

Blumenthal, like some consumer groups and other lawmakers, also urged GM on Thursday to compensate drivers and families of victims of accidents related to the defective ignition switches.

Senate and House of Representatives committees next week kick off public hearings on GM's handling of product recalls for 1.6 million vehicles.

The recalls came last month even though GM first noticed potential problems with its ignition switches in 2001 and subsequently heard repeated warnings from consumers.

The defective switches have been linked to 12 deaths.

Also on Thursday, a federal judge in Corpus Christi, Texas, scheduled a hearing for April 4 on a request for a court order directing GM to notify customers to stop driving recalled vehicles immediately.

The request was made by Robert Hilliard, a lawyer for Charles and Grace Silvas, who own a 2006 Chevy Cobalt. They are suing GM for allegedly concealing the ignition defect for more than a decade, which they said caused recalled vehicles to lose value.