The NBA’s squarely in the sights of the United States Department of Justice over accusations The Association worked to torpedo Ice Cube‘s Big3 basketball league … allegations the NBA denies.

TMZ Sports has learned the DOJ launched the inquiry months ago, examining Alleged Anticompetitive Behavior on the part of the NBA, aimed at squashing the Big3‘s growth.

Those allegations, we’re told, range from the NBA purportedly throwing its weight around to prevent sponsors and others potential partners from doing business with the rap legend’s league … to discouraging television networks from carrying Big3 games.

Cube and business partner Jeff Kwatinetz launched the 3-on-3 league, made up almost entirely of retired NBA players, in 2017.

Some current players have expressed a desire to play in Cube’s league in the offseason, but we’re told, as the Big3 sees it, the NBA has prevented guys from doing so, putting arbitrary rules in place to stop players from hooping in Ice’s league.

FYI, the NBA and Big3 seasons do not overlap.

Of course, it’s a regular occurrence for NBA players, including some of the biggest stars in the world like LeBron James, to hoop in non-NBA games after the season ends … such as L.A.’s famed Drew League.

Big3 officials, according to sources familiar with the investigation, believe they’ve been unfairly targeted by the NBA.

We’ve also been told NBA owners have been discouraged from investing in the Big3 while simultaneously owning a franchise.

Referees haven’t been immune, either, according to a source … who says they’ve been told they cannot officiate for the Big3, despite some working for other organizations outside of the NBA.

A source familiar with the Dept. of Justice investigation tells us Cube and Kwatinetz met with DOJ lawyers during the first half of the year. We’re also told investigators have begun reaching out to NBA owners as part of their investigation.

If the government ultimately finds the league committed antitrust violations, the NBA could face a significant fine.

We reached out to the league for comment … and NBA spokesman Mike Bass, addressing the allegations of sponsorship and TV network interference, pressuring potential Big3 partners, and others, told us, “Those claims are not true.”

Bass also added … “We have been supportive of the Big3 since its inception, but we declined to invest.”