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Donald Trump’s newly minted convention manager on Sunday accused Republican presidential rival Ted Cruz’s campaign of “Gestapo tactics” and of “not playing by the rules” in its efforts to wrangle the support of Republican delegates.

Paul Manafort, a veteran Republican operative who managed the convention efforts of several successful presidential campaigns, was tasked earlier this week by Trump with directing the campaign’s new delegate-focused campaign strategy.

Manafort said the Trump campaign’s strategy won’t involve threatening delegates, but accused Cruz of employing those tactics, which he referenced by alluding to the notorious Nazi Germany secret police force.

“He’s threatening,” Manafort said of Cruz on NBC’s “Meet the Press.” “You go to these county conventions, and you see the tactics, Gestapo tactics, the scorched-earth tactics.”

Trump on Sunday tweeted, “I win a state in votes and then get non-representative delegates because they are offered all sorts of goodies by Cruz campaign. Bad system!”

Cruz campaign spokeswoman Catherine Frazier dismissed the complaints as “sour grapes.”

“More sour grapes from Trump who continues to lash out in tantrums every time he loses. We are winning because we’ve put in the hard work to build a superior organization,” she said.

She added: “We have earned our success by working hard to build a superior organization and are working within the process and rules that have been established – which has led now to four consecutive wins, 12 wins total.”

Manafort also conceded that while he believes Trump will have a clear “path” to clinching the Republican nomination by mid-May, the billionaire candidate will need to “go through June” and “wait ‘til the process is done” to cross the 1,237-delegate threshold necessary to capture the nomination on the first ballot at the convention.

Manafort also sought to downplay reports in the last week of a power struggle within the Trump campaign after Trump expanded Manafort’s role and responsibilities shortly after hiring him and after Manafort said he reported “directly” to Trump – and not to campaign manager Corey Lewandowski.

“A lot of what’s being talked about is much ado about nothing. Yes, there’s a transition, it’s a natural transition. Trump was doing very well on a model that made sense, but now, as the campaign has gotten to the end stages, a more traditional campaign has to take place,” Manafort said.

CNN’s Ashley Killough contributed to this report.