US Republican mega-donor and hard-line Zionist Sheldon Adelson will be contributing more than ever to help presumptive GOP presidential nominee Donald Trump get elected in November, a report says.

Adelson told Trump in a private meeting last week that he was willing to spend $100 million for his presidential campaign, two Republicans with direct knowledge of the casino mogul’s commitment, told the New York Times. The report was published on Friday.

Adelson has decided to significantly scale back on his donations to the congressional Republicans to boost Trump’s chances of being elected, the report said.

The two men met at a hotel in New York and Adelson formally endorsed Trump on Friday. During the meeting, Trump reportedly stressed that he is committed to the security of Israel.

Adelson, who together with his wife spent nearly $100 million in the 2012 presidential campaign cycle, is known to be a major supporter of Israel and its Prime Minister Benjamin Netanyahu.

Sheldon Adelson (left) and his wife Miriam Adelson are standing with Benjamin Netanyahu.

Adelson had previously voiced support for Trump, but in a Washington Post article on Friday, he “strongly encourage[d]” those still on the fence about the divisive billionaire to do likewise.”

The multi-billionaire wrote that Trump “exemplifies the American spirit of determination, commitment to cause and business stewardship.”

“You may not like Trump’s style or what he says on Twitter, but this country needs strong executive leadership more today than at almost any point in its history,” Adelson wrote.

“For nearly eight years, Republicans have fought tooth and nail against President Obama and his policies. We waged battles over debt, government spending, Obamacare and the Iran nuclear deal — an issue of paramount importance to me personally and to many others around the world … If Republicans do not come together in support of Trump, Obama will essentially be granted something the Constitution does not allow — a third term in the name of Hillary Clinton,” he added.

Adelson, the CEO of the Las Vegas Sands casino group, was listed by Forbes in June 2015 as having a fortune of $28 billion, making him the 18th richest person in the world.

He is a major contributor to Republican Party candidates, which has resulted in his gaining significant influence within the party.

Adelson, a Zionist Jew, has said his most important issue when considering which candidates to support in US elections is “the safety of Israel.”

Adelson had previously expressed interest in Florida Senator Marco Rubio and his wife Miriam liked Texas Senator Ted Cruz.

Donald Trump arrives at the Republican National Committee (RNC) headquarters on Capitol Hill in Washington, DC, on May 12, 2016. (AFP photo)

But after Trump's commanding victory in Indiana's primary earlier this month, his remaining challengers, Cruz and John Kasich, both suspended their presidential bids, leaving the businessman tycoon on an uncontested path to the Republican nomination.

Rubio dropped out of the presidential race in March after losing the Florida primary to Trump and failing to unite the Republican establishment against the billionaire businessman.

Trump’s campaign has been marked by controversial statements, including with disparaging remarks about Mexican immigrants and Muslims.