WASHINGTON (Reuters) - The White House said on Thursday it will establish 48 national electric-vehicle (EV) charging networks on nearly 25,000 miles of highways in 35 U.S. states.

A Kia Soul EV is plugged into a charging station during the second press day of the North American International Auto Show in Detroit, Michigan, January 13, 2015. REUTERS/Mark Blinch

The Obama administration said 28 states, utilities and vehicle manufactures, including General Motors Co GM.N, BMW AG BMWG.DE and Nissan Motor Co 7201.T, and EV charging firms have also agreed to work together to jump-start additional charging stations on the corridors.

The corridors were required to be established by December under a 2015 highway law.

The Federal Highway Administration on Thursday unveiled new roadside signs to help motorists find charging stations. The White House said drivers can expect either existing or planned charging stations within every 50 miles.

It also said 24 state and local governments have agreed to buy hundreds of additional electric vehicles for government fleets and add new EV charging stations. Overall, the number of U.S. charging stations has grown from 500 in 2008 to more than 16,000, the White House said.

California will buy at least 150 zero-emission vehicles and provide EV charging at a minimum of 5 percent of state-owned parking spaces by 2020.

The city of Atlanta will add 300 charging stations at Hartsfield-Jackson International Airport by the end of 2017.

Los Angeles agreed to nearly triple the city’s current plug-in electric fleet to 555 vehicles from about 200 by the end of 2017. Of those, 200 will be for the police department. The city is also adding another 500 charging stations by 2017.

One hurdle to the mass adoption of EVs has been the difficulty in finding places to recharge vehicles. In July, the White House said it was expanding a federal loan guarantee program to include companies building EV charging stations.

The Energy Department issued a notice clarifying that charging facilities, including hardware and software, are an eligible technology for the $4.5 billion loan program. But no loans have been made for EV charging projects yet, officials said on Thursday.

Administration efforts come as U.S. EV sales have not met early expectations. Sales have fallen well below President Barack Obama’s goal of 1 million by 2015.

U.S. Energy Secretary Ernest Moniz told Reuters in January that the country may hit the figure in three to four years with continuing improvements in battery technology, but he acknowledged low gasoline prices have hurt EV sales.

In August 2008, Obama set a goal of getting 1 million plug-in electric vehicles on the roads by 2015. Only about 520,000 electric cars have been sold in the United States since 2008, out of about 250 million cars and trucks on U.S. roads.

The White House has repeatedly tried to boost EV sales, including hiking the EV tax credit and converting it to a point-of-sale rebate, but the proposals have yet to pass Congress.

Electric vehicle infrastructure will also get a boost from Volkswagen AG's VOWG_p.DE diesel emissions settlement. The German automaker must spend $2 billion over 10 years to improve infrastructure and other efforts to advance zero emission vehicles.