WASHINGTON, Dec. 3 (Xinhua) -- U.S. President Donald Trump's top economic adviser said Monday that the administration is planning to revoke federal tax credits for all electric vehicles, broadening the president's earlier threat targeting automaker General Motors (GM).

"As a matter of our policy, we want to end all those subsidies," Lawrence Kudlow told reporters, adding that the plan under consideration is to undo "other subsidies imposed during the Obama administration."

When asked about a specific timeline, the director of the White House National Economic Council said it will be done by 2020 or 2021.

The latest development followed Trump's threat last week that his administration will pull all subsidies for GM, which earlier announced plans involving massive job cuts and factory shutdowns in North America and beyond.

To further explain Trump's intention, Kudlow said the president was referring to a stimulus package during the administration of former President Barack Obama which granted a 7,500-U.S.-dollar tax break to consumers buying electric cars.

Although the policy directly benefits the consumers, it effectively reduces costs for electric vehicle manufacturers.

The question remains as to whether the Trump administration has the authority to nullify the incentives, since the stimulus package has become a piece of legislation, meaning any action to change it requires due process in Congress.

Experts also doubted the possibility that Trump can get it done via executive order.

One stipulation of the tax credit is that it will phase out once an automaker's production of electric vehicles reaches a cap of 200,000.

GM is closing in on the threshold, having less than 4,000 vehicles to produce as of the third quarter of 2018.

U.S. lawmakers as well as a coalition of automakers, including GM and Tesla, have sought to extend the tax credit by raising the current cap.