Donald Trump says he will easily win the Republican presidential nomination if John Kasich drops out of the contest.
Mr Trump, the Republican front-runner, said the Ohio governor should not stay in the contest because he could not collect enough delegates to win.
His comments came just ahead of Tuesday's Wisconsin vote, which could reshape the Republican race.
"If I didn't have Kasich, I automatically win," Mr Trump said at a rally in Wisconsin.
If Mr Kasich did quit the race, he would be following on the heels of former Florida Governor Jeb Bush and Florida Senator Marco Rubio.
The Ohio Governor said in response to Mr Trump he would stay because no one would get the required number of delegates to win outright.
"Since he thinks it's such a good idea, we look forward to Trump dropping out before the convention," Kasich spokesman Chris Schrimpf said.
If, as polls were suggesting, Mr Trump lost the primary contest on Tuesday he would be far less likely to have the all-important 1237 delegates needed to secure the nomination.
Delegates represent their states at the party's convention and are collected by candidates via the votes in each state.
Mr Trump's count stood at 735 delegates, Texas Senator Ted Cruz had 461 and Mr Kasich trailed with 143.
If no one hit 1237 after all 50 states had voted, the Republican convention in July would be contested.
That would mean the delegates voting for a nominee, and Mr Trump's unpopularity among sections of the party could lose him the nomination.
New York businessman Mr Trump had just weathered a very difficult seven days in which he sparked outcry with comments about abortion, stood by his campaign manager who was charged with assaulting a reporter, and raised eyebrows with remarks about US foreign policy and economy.
"Was this my best week? I guess not," Mr Trump told Fox News Sunday.
A loss in Wisconsin, the kind of state he had done well in up to now, would raise questions about whether his campaign was running out of steam.
He met the Republican National Committee (RNC) in Washington to review delegate and party rules days after breaking a promise made to them that he would back the eventual nominee.
Mr Kasich has recognised that he will not be able to gain enough delegates before the convention.
Reince Priebus, president of the RNC, has said the nominee will be someone who is running, but acknowledged that a brokered convention is a possibility.
The Democrats are campaigning ahead of Wisconsin's primary as well, where Hillary Clinton is hoping to hold off a resurgent Bernie Sanders.