US Republican presidential candidate and Ohio Governor John Kasich speaks at a media event during the Republican National Committee Spring Meeting at the Diplomat Resort in Hollywood, Florida, April 20, 2016. [Photo/Agencies]

"Donald Trump doesn't have the support of a majority of Republicans -- not even close, but he currently does have almost half the delegates because he's benefited from the existing primary system," Weaver said.

"Our goal is to have an open convention in Cleveland, where we are confident a candidate capable of uniting the Party and winning in November will emerge as the nominee," Weaver was quoted by a TheHill news daily report as saying.

Trump blasted the arrangement shortly after it was announced. On his Twitter, the real estate tycoon said: "Wow, just announced that Lyin' Ted and Kasich are going to collude in order to keep me from getting the Republican nomination. DESPERATION!"

In the latest Indiana polling carried out by Fox News, Trump, having won 845 delegates so far, now holds just an 8-percent lead over the Texan senator who has 559 delegates in his pocket, while Kasich sits far behind.