Republican presidential candidate Donald Trump has responded to GOP rival Ted Cruz's suggestion that he and Marco Rubio's opposition to marriage equality is weak.

Cruz took aim at his rivals while speaking at the Carolina Values Summit at Winthrop University on Thursday.

While Trump and Rubio have said that they oppose the Supreme Court's June finding that gay and lesbian couples have a constitutional right to marry, they've also said that they would abide by the “law of the land.”

“Those are the talking points of Barack Obama,” Cruz said.

“Lying Cruz put out a statement, 'Trump & Rubio are w/Obama on gay marriage.' Cruz is the worst liar, crazy or very dishonest. Perhaps all 3?” Trump tweeted on Friday.

“How can Ted Cruz be an Evangelical Christian when he lies so much and is so dishonest?” he added.

Later in the day, Trump threatened to sue Cruz “for not being a natural born citizen.”

(Related: Donald Trump won't say how appointing judges opposed to gay marriage would unify Americans.)