By Hyunjoo Jin and Trevor Hunnicutt

(Reuters) -Tesla's electric-vehicle charging technology is being put on a fast track to become a U.S. standard, the automotive industry group of engineers that reviews standards said on Tuesday.

Tesla's charging technology has been gathering momentum for weeks. Volvo on Tuesday joined General Motors, Ford and Rivian in embracing Tesla's charging design, shunning earlier efforts by the Biden administration to make the Combined Charging System (CCS) the dominant charging standard in the United States.

Tesla calls its technology "the North American Charging Standard (NACS)," but it has yet to be approved as a U.S. standard.

Tesla shares were up 2.3% on Tuesday.

"The new SAE NACS connector standard will be developed on an expedited timeframe and is one of several key initiatives to strengthen the North American EV charging infrastructure," SAE International, a standards-developing organization for engineers, said in a statement on Tuesday.

The United States is on track to install a network of 1.2 million electric-vehicle public chargers, including 1 million Level 2 chargers, by 2030, according to a study by the National Renewable Energy Laboratory (NREL), a federally funded research center. The study provided no breakdown of NACS and other types of connectors.

This projection exceeds the Biden administration's goal to deploy 500,000 public chargers by 2030.

Building out the public charging network will require between $33 billion and $55 billion of cumulative public and private capital investment, according to the NREL study.

The Biden administration's approach to CCS and NACS connectors is facilitating "more interoperable, and ultimately a more accessible set of chargers across the country," the White House national climate adviser, Ali Zaidi, told Reuters on Tuesday.

The White House has said electric-vehicle charging stations using Tesla-standard plugs would be eligible for billions of dollars in federal subsidies as long as they included the U.S. charging standard connection, CCS, as well.

The states of Texas and Washington have said they will mandate the NACS, along with CCS, as part of the federal program.

(Reporting by Hyunjoo Jin in San Francisco and Trevor Hunnicutt in WashingtonWriting by Peter HendersonEditing by Matthew Lewis)