WASHINGTON — (CNN) Donald Trump on Monday slammed Ted Cruz and John Kasich for teaming up to deny him the Republican presidential nomination, calling the effort “weak” and “pathetic.”

“Did you see the news today, where they band together? Where they collude? It’s collusion,” Trump told his supporters at a rally in Warwick, Rhode Island.

He called the alliance another example of “corruption” in politics.

“If you collude in business … they put you in jail. But in politics … you’re allowed to collude,” he said.

But he said he welcomed the news as further evidence that his GOP primary opponents can’t keep up with him.

“Actually I was happy, because it shows how weak they are, it shows how pathetic they are,” Trump said, calling them by his favorite nicknames: “Lyin’ Ted” and “1 for 41 Kasich.”

The Cruz-Kasich partnership is roiling Republican politics one day before voters go to the polls in Rhode Island, Maryland, Delaware, Connecticut and Pennsylvania.

Trump is poised to perform well in those states but Cruz and Kasich are focused on later contests.

In statements released minutes apart late Sunday, Cruz’s campaign said it would cede New Mexico and Oregon to Kasich and focus instead on Indiana, all in a last-ditch effort to deny Trump the 1,237 delegates he needs to lock down the GOP nomination.

Kasich and Cruz said Monday the rationale for their decision to coordinate campaign strategy — for now — is an effort to stop Trump from winning the Republican nomination because they fear he would lose to Hillary Clinton in a general election matchup.

The two candidates unveiled nearly identical talking points in defending their decision to strategically invest in states and stay out of each others’ way — even as they took shots at each other.

“What’s the big deal?” Kasich said at a Philadelphia diner on Monday as reporters peppered him questions about his decision to skip campaigning in Indiana, ceding the territory to Cruz.

But Kasich refused to say he would encourage his supporters to vote for Cruz in Indiana.

“They ought to vote for me,” he said during the gaggle.

Kasich’s chief strategist tweeted that voters “get it” — implying that they’ll make the right decision on how to vote in next week’s primary.

“We’re not telling voters who to vote for in IN, only where we are going to spend resources to ultimately defeat Hillary. They get it,” John Weaver tweeted.

The governor himself brushed off the interest in the two campaigns’ sudden decision to map out a mutually beneficial course — and criticism that it was an inappropriate alliance.

“I’m not campaigning in Indiana and he’s not campaigning in these other states, that’s all. It’s not a big deal,” Kasich said.

Meanwhile, the Texas senator on Monday praised his opponent for getting out of his way in the Hoosier State, which votes next week, calling it important in the effort to stop the GOP front-runner Trump.

“After discussions with the Kasich campaign, we made a decision to allocate our resources,” he told reporters in Indiana. “I think that made sense for both campaigns.”

Cruz repeated the message from his campaign that it is focusing its resources strategically and investing heavily in Indiana, citing a desire to stop Clinton from winning the White House.

Kasich stuck to that talking point as well, telling reporters the goal was entirely to stop Clinton and he was simply making choices with his resources.

He said Trump would not be able to beat Clinton in November.

Trump, though, said neither could beat Clinton.

“I will beat Hillary Clinton,” Trump said. “Lyin Ted Cruz will lose so badly to Crooked Hillary it will be one of the great defeats ever, and Kasich will also as soon as they put up the negative ads.”

The move comes as both men would only be able to capture the GOP nomination at a contested convention, where no candidate gets 1,237 on the first ballot. Kasich has been mathematically eliminated from contention for weeks, and after last week’s romp for Trump in New York, it is essentially impossible for Cruz, as well.

But after delegates cast their first ballots in July, many become free agents to vote for whomever they choose, regardless of results in their state primaries — and that gives Cruz and Kasich opportunity to still end up the nominee.

Both candidates said their campaigns had conversations with each other, and that they agreed on a resource strategy that made sense.

They also both spoke of a contested convention as a foregone conclusion.

“We’re going to a convention, it’s going to be an open convention,” Kasich said, denying anything unfair about the effort. “All you’ve got to is get the right number of delegates, and you win. If you don’t get the number of delegates, you don’t win.”

“It is abundantly clear that nobody is getting to 1,237, we are heading to a contested convention, and at a contested convention, Donald Trump is in real trouble,” Cruz said.

Trump, for his part, blasted the coordination in a storm of tweets Sunday night and Monday, saying it was a desperate move.

“Wow, just announced that Lyin’ Ted and Kasich are going to collude in order to keep me from getting the Republican nomination. DESPERATION!” Trump wrote Sunday night.

Kasich and Cruz similarly shrugged off the idea that the move was a hail Mary.

“There is desperation on the Trump side,” Cruz said, saying that Trump will “cry and whine” because he’s a “sore loser.”

And Kasich protested by turning a reporter’s question back around, saying, “No, I’m not desperate, are you? Are you desperate? Because I’m not.”