Republican party presidential candidates Ted Cruz and John Kasich have agreed to coordinate in a last-ditch effort to deny frontrunner Donald Trump the party's nomination for US president.
Cruz plans to stop campaigning for the Oregon and New Mexico primaries to help Kasich, while the latter will give Cruz a "clear path" in Indiana.
"Having Donald Trump at the top of the ticket in November would be a sure disaster for Republicans," Cruz's campaign manager, Jeff Roe, said.
"Not only would Trump get blown out by Clinton or Sanders, but having him as our nominee would set the party back a generation."
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Kasich's chief strategist John Weaver said that Kasich's goal was to have no candidate win the number of delegates required to clinch the nomination, which would lead to an open nominating contest at a Republican National Committee convention scheduled for Cleveland in July.
"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 said.
'Dead and desperate'
Trump, a billionaire property tycoon and reality television star, in a series of tweets said the announcement was a sign of desperation.
"Lyin' Ted and Kasich are mathematically dead and totally desperate. Their donors & special interest groups are not happy with them. Sad!" he said .
Trump has a clear lead in delegates with 846 compared with 563 for Cruz and 147 for third-placed Kasich.
But he may still fall short of the 1,237 needed to win outright. If he does not reach that target, the vote would come down to a contested convention, where a different nominee could emerge through negotiations among party figures.
Republicans in the northeastern states of Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island go to the polls on Tuesday. Trump is predicted to be the leading candidate in all of those states.