NEW YORK, NOV. 19 -- U.S. Attorney Rudolph W. Giuliani has received assurances from Donald J. Trump, one of New York's wealthiest and most prominent developers, that Trump will help him raise funds if the prosecutor decides to challenge Sen. Daniel Patrick Moynihan (D-N.Y.) next year.

Asked today whether he would help Giuliani raise money in the real estate world, Trump said: "If Rudy decides to run for public office, I hold Rudy in very high esteem and I would love to be helpful to Rudy.

"Rudy is a man who has tremendous talents," Trump said. "The development community should love Rudy because Rudy's gone after organized crime and other things that adversely affect the development community."

Trump's financial talents are in demand in other quarters these days. Earlier this week, House Speaker Jim Wright (D-Tex.) asked Trump, a Republican, to chair the annual Democratic congressional fund-raising dinner. Trump said he is considering the request.

Giuliani said he has not decided whether to resign as U.S. attorney in Manhattan and seek elective office. He said he would not resign unless he could ensure that there would be "no loss of momentum" on organized crime and political corruption investigations in which he has been personally involved.

Giuliani has discussed a possible race for Moynihan's seat with Sen. Alfonse M. D'Amato (R-N.Y.) and other Republicans. Giuliani said he has not spoken directly with Trump but has "heard" of Trump's willingness to support him and was "flattered."

He declined to discuss potential fund-raising in detail but joked: "Some people say I have cut out the two most logical sources of money in New York: Wall Street and the Mafia."

Two major grand jury probes of insider stock trading and financial corruption involving three Wall Street firms -- Goldman Sachs & Co., Kidder Peabody & Co. and Drexel Burnham Lambert Inc. -- are unlikely to be completed before the end of the year.

The other major Republican who is considering the Senate race is Ronald Lauder, former U.S. ambassador to Austria. As heir to a perfume fortune, Lauder would have little problem financing his campaign.

The possibility that Giuliani may jump into the political arena has touched off intense jockeying for his job, according to lawyers familiar with the selection process. They said that D'Amato, who would recommend Giuliani's replacement to President Reagan, is considering some attorneys who represent clients in the Wall Street probes.

Candidates under discussion include Dennison Young and Howard Wilson, two top Giuliani aides, and securities lawyers John Wing and Gerald Walpin, sources said.

In the 4 1/2 years since he resigned as associate attorney general to become U.S. attorney here, Giuliani has become the country's best known federal prosecutor. He has displayed a flair for publicity while winning convictions of top Mafia leaders, prominent stockbrokers and corrupt New York city politicians.

Bill Cunningham, a Democratic political consultant, said Giuliani "is kind of the media darling in New York. His image is very clean-cut: the prosecutor going after the bad guys." Giuliani's Italian-American heritage also would be a big plus with ethnic voters, Cunningham said.

But he said Giuliani is "an unknown quantity" on most issues and "has never been through a tough campaign."

By most assessments, Moynihan, a two-term senator and former U.N. ambassador, will be difficult to unseat. Although he is occasionally faulted for not spending enough time in New York, Moynihan is an internationally known scholar and the chairman of key subcommittees on Social Security and public works.

"The issues that will determine the Senate race should be Pat Moynihan's issues: the federal budget, arms control, the poor, Social Security," Cunningham said.

While there is widespread resentment on Wall Street of Giuliani's aggressive tactics, Giuliani said bankers and brokers have applauded his probes and might support him. As for labor support, the one major union that often supports Republicans -- the Teamsters -- is the potential target of a racketeering lawsuit by Giuliani's office to place it under federal control.