The Federal Trade Commission has green-lighted General Motors' purchase of Cruise Automation, a Silicon Valley startup that makes the technology behind self-driving cars.
The FTC and Justice Department has granted the transaction "early termination", or quick antitrust approval.
The acquisition of Cruise Automaton - which has only 40 employees - has been reported to be worth over $1bn in cash and stock, but the Detroit car maker has not released the purchase price.
Announced in early March, the deal sets GM against Google, Toyota and Tesla in the driverless car market.
Kyle Vogt, founder of Cruise Automation, said:
GM's commitment to autonomous vehicles is inspiring, deliberate, and completely in line with out vision to make transportation safer and more accessible.We are excited to be partnering with GM and believe this is a ground-breaking and necessary step toward rapidly commercialising autonomous vehicle technology.
Cruise Automaton was founded three years ago and been testing its software in San Francisco.
GM has also been showing wider interest in tech companies, investing $500m in ride-sharing company Lyft in January this year.
The US car maker has also started a car-sharing service in Ann Arbor, Michigan, which is expected to expand.