WASHINGTON — The federal government would provide grants to help cities build the infrastructure needed to support electric vehicles and to offer new tax credits for buyers of those cars under legislation introduced Thursday in Congress.

The bills in the House and Senate are designed to smooth the way for the electric vehicles that are expected to start showing up at car dealerships in large numbers this fall. Supporters hope to add 700,000 vehicles to the road that are powered largely by electricity in the next several years.

The legislation will lead to "broad-based deployment of electric vehicles in this country," said Sen. Byron Dorgan, D-S.D., one of the main sponsors of the Senate version.

The government has several programs to spur the development of vehicles that use little or no gasoline. That includes federal tax credits of up to $7,500 for the purchase of an electric vehicle and up to $25 billion in loans earmarked for manufacturers of alternative fuel technologies.

The Senate bill would allow up to 15 municipalities and cities to apply to the Department of Energy for grants of up to $250 million to build infrastructure such as public recharging stations. The House version offers $800 million to five communities.

The Senate would let buyers in those areas to take an additional $2,500 credit for the purchase of an electric vehicle, bringing the total credit to $10,000. The House version gives a credit of up to $2,000 for electric vehicle owners to buy and install charging equipment.

The Senate version also proposes $1.5 billion for research with the goal of inventing technology such as a battery that can go 500 miles on a single charge.