Donald Trump is threatening Sunday to sue Ted Cruz over taking his Louisiana delegates, the Republican presidential frontrunner said Sunday.

"Just to show you how unfair Republican primary politics can be, I won the State of Louisiana and get less delegates than Cruz-Lawsuit coming," Trump tweeted Sunday afternoon.

In the Louisiana primary March 5, Trump won the popular vote, 124,818 votes to 113,949 for Texas Sen. Ted Cruz. Florida Sen. Marco Rubio tallied 33,805 votes — having since dropped out of the race — and Ohio Gov. John Kasich had 19,355.

Originally, Trump and Cruz each got 18 delegates, with five going to Rubio.

But as the Wall Street Journal reported earlier this week, Cruz may wind up with as many as 10 more delegates from the state than Trump because he has out-hustled him in the delegate selection process.

WSJ also reported that Cruz's supporters "also seized five of Louisiana's six slots on the three powerful committees that will write the rules and platform at the Republican National Convention and mediate disputes over delegates' eligibility this summer in Cleveland."

While delegates won in a state are pledged to back the winner on the first ballot at the convention, Cruz has been working hard to assure many of the delegates freed to switch their vote on the second ballot will back him. Trump has been slow to see this threat. The Wall Street Journal story said Trump's campaign was unaware of his losses in Louisiana until the paper contacted him.

Earlier Sunday, Trump called the Republican election system for how delegates are awarded "crooked" and "rotten" in an appearance on ABC's "This Week."

Trump's threat drew wide mockery.

"He should sue his own campaign for not knowing some of the basics of delegate rules," tweeted Dan Pffieffer, a former top political aide to President Obama.

Cruz staffers joined in later Sunday.

"Maybe your time is better spent reading rules than sending hate-tweets," tweeted Cruz national spokesman Ron Nerhing.

Oh cry me a river…we have earned our delegates fair & square, & our momentum grows…rightfully troubling to Trump," added Catherine Frazier, Cruz's press secretary.

Trump claim that he plans a lawsuit also came just minutes after he reacted to a terror attack that killed scords of woman and children in Lahore, Pakistan, with the assertion: "I alone can solve."

The dueling tweets raise the question of how Trump can solve radical terrorism in Pakistan if he can't handle party politics in Louisiana.