Facing a potential wipeout in U.S. presidential nominating contests on Tuesday, Republicans Ted Cruz and John Kasich teamed up against Donald Trump, setting off a barrage of new attacks from the front-runner who denounced them as desperate, weak and pathetic.

Trump told a cheering crowd in Warwick, Rhode Island, on Monday that he was happy about the partnership. "It shows how weak they are. It shows how pathetic they are."

Cruz, a U.S. senator from Texas and Trump's closest challenger, said the move was aimed at preventing a Trump nomination that would assure victory for Democrat Hillary Clinton in the Nov. 8 presidential election.