US Republican presidential candidate Donald Trump gives the thumbs up as he takes the stage to speak at a campaign event in Buffalo, New York, US, April 18, 2016. [Photo/Agencies]

Trump has 744 delegates to 559 for Cruz and 144 for Ohio Governor John Kasich, according to the Associated Press. That count includes endorsements from several delegates who are free to support the candidate of their choice.

New York's contest comes after Cruz was awarded all 14 delegates in Wyoming's nominating contest, the latest state-by-state delegate battle, according to a party official on Saturday.

"Lyin' Ted Cruz can't win with the voters so he has to sell himself to the bosses-I am millions of VOTES ahead! Hillary would destroy him & K," Trump tweeted on Monday, also referring to Kasich.

Cruz, speaking on ABC's "Good Morning America" in Times Square, responded to Trump by saying his rival was throwing a fit because he has lost several recent state contests.

"The stakes are too high to hand the election to Hillary Clinton, which is what nominating Donald Trump (would do)," he told ABC.

Cruz also defended his "New York values" remark, which he had used in an attack on Trump months ago. He said on Monday that New Yorkers had "suffered under the left-wing Democratic policies" of New York City Mayor Bill de Blasio and Governor Andrew Cuomo.

While Cruz campaigned in New York City, Trump was to hold a rally in Buffalo, Cruz will campaign in New York City. Kasich will be in Syracuse and Schenectady, two upstate New York cities.

Sanders needs to defy expectations with a strong victory in the state if he is to overtake Clinton. In New York, 291 convention delegates are at stake.

Clinton, who needs 2,383 delegates to win the Democratic nomination, has 1,758 to Sanders' 1,076, according to AP. That total includes unpledged superdelegates who are free to back the candidates of their choice but told the news service whom they support.

Clinton, a US senator from New York for eight years, initially held a 30-percentage-point lead in opinion polls over Sanders, a Brooklyn native. But Sanders has cut that advantage by about two-thirds after an unbroken string of victories in the last eight state nominating contests.

On Monday, Sanders acknowledged that polls still showed him behind Clinton but told NBC's "Today" program: "Let's look at the real poll tomorrow."

Sanders drew about 28,000 people to Brooklyn's Prospect Park on Sunday, according to his campaign. He is hoping for more crowds at a concert and rally at a park alongside the East River in the New York City borough of Queens on Monday evening.

In addition to Yonkers, Clinton will campaign in Manhattan on Monday. Her husband, former President Bill Clinton, will head upstate to Buffalo and Rochester.