By Thursday, five of the 11 states that also seek stricter auto emission standards -- Pennsylvania, Connecticut, Maryland, Oregon and Rhode Island -- had sent letters to the EPA in support of California's threat, said Frank O'Donnell of the group Clean Air Watch.

The EPA had agreed Tuesday to consider California's request to limit tailpipe emissions and hold a hearing May 22 in Washington.

The suit already filed regarding washing machine efficiency standards contests the DOE's 2004 denial of a waiver to federal standards requested by the state energy commission.

The suit was filed last Friday with the US Ninth Circuit Court of Appeals in San Francisco.

The DOE contends that California did not meet requirements for the granting of a waiver, said agency spokeswoman Julie Ruggiero.

A waiver request has to be justified economically and be technically feasible, she said.

"We are committed to increasing efficiency on a variety of fronts, but you have to meet the law in order to change the law," Ruggiero said. "In California, if we were to change the standard that high, that quickly, it could have a negative impact on the producer and the consumer."

The more water-efficient machines will cost about US$130 more, but savings on water and energy will save the average consumer about US$242, the energy commission said.

"For a state that faces perpetual water issues, every drop counts," said Commission Chair Jackalyne Pfannenstiel in a press statement by the energy commission. "Less water use in California clothes washers will eventually save enough to supply a city the size of San Diego every year."

The state would also save lots of electricity and natural gas, as well as cut climate-changing greenhouse gas emissions, the suit claims.

California in 2002 established standards to require washing machines sold after 2007 to use no more than 8.5 gallons per cubic foot of washing machine capacity. The standard would then become a tougher 6 gallons per cubic foot by 2010.