Ice Cube is suing a trio of Persian Gulf investors for $1.2 billion, claiming they tried to seize control of his fledgling Big3 basketball league even as they broke promises to fund it.

The suit by the legendary rapper and his talent-agent partner Jeff Kwatinetz alleges that the investors, connected to the royal family of Qatar, ponied up only a third of their $20.5 million commitment to Big3.

That, in turn, has crippled efforts to elevate the league’s 3-on-3 basketball games with former NBA stars like Allen Iverson, Julius Erving and Amar’e Stoudemire “to the professional setting of NBA-style arenas and broadcast games,” according to the suit.

“These members and associates of the royal family made excuse after excuse for not paying, all of which is documented in text messages and emails,” according to the suit filed Thursday in Los Angeles Superior Court.

“The blame for their failure to fund the millions they owed the BIG3 ran the gamut from their ‘sinuses,’ ‘hiking,’ it being a ‘long day bro,’ and to bad press regarding Qatar associations with alleged funding of terrorism,” the suit alleged.

The strained relationship reached a breaking point in February when Ahmed Al-Rumaihi, a trio member who once served as a Qatar diplomat to the US, demanded a 25 percent ownership stake and a show of respect for the investor’s status as “a royal family member,” according to the suit.

“You don’t know who I know in LA and what they’re capable of!” al-Rumaihi allegedly screamed after Kwatinetz responded by demanding cash that was already owed, the suit alleges. “You should think of your safety and the safety of you and your family.”

The suit — which twice presents itself as “a cautionary tale” against partnering with the Qatari investors — accused another defendant of trying to defame Kwatinetz by claiming he called the league’s African-American players “Rich Nigg*s.”

The defendant, Ayman Sabi, admitted he didn’t personally hear Kwatinetz use the phrase, according to the suit — but claimed a “former employee” did. The suit then quotes a text message between Ice Cube and the former employee, who writes, “I never said that!!!”

Before exposing themselves as deadbeats, Big3’s Qatari investors reveled in being associated with the league, treating employees to “trips to St. Tropez and Ibiza, parties on yachts, expensive meals, use of their exotic cars, invitations to parties at their Los Angeles mansions, and investments in personal business projects unrelated to the Big3,” according to the suit.

They even rented three mansions in the Los Angeles neighborhoods of Venice, Malibu and Beverly Hills — “so they could be near the Big3 founders and employees,” the suit states.

Big3’s co-founders claim reputational harm and damages that work out to about $20 million per Big3 player — each of whom receives a share of the league’s overall revenue.

Although The Post could not reach the defendants for comment, The Washington Post, which broke the story, quoted a spokesman who dismissed the suit as a “blatantly false and malicious fabrication.”

The case for Big3 and its co-founders is being headed by Mark Geragos, who’s also a Big3 investor. The Los Angeles lawyer has also represented pop star Michael Jackson, actress Winona Ryder and politician Gary Condit.