Republican presidential front-runner Donald Trump attacked his top Democratic rival Hillary Clinton on Friday, calling her "crooked", and promised his supporters that he would not become overly presidential.

The comments undercut what his aides had said would be an attempt by the notoriously blunt-speaking Trump to project a more serious image, including by rolling out more policy details in the coming days.

"I can tell you that if I go too presidential, people are going to be very bored," the New York real estate baron told Fox News in an interview that will air on Saturday. The network released excerpts on Friday.

He went on to say that Clinton "is a person who's got many, many flaws" and that she's "the worst possible representative a woman can have," as he shifted his focus away from Republican rivals and toward the Nov. 8 general election.

"The only thing she's got going is the women card," Trump said. "We call her 'Crooked Hillary' because she's a crooked person. She's always been a crooked person."

Clinton said at an event on Friday in Jenkintown, Pennsylvania, that she would not respond to Trump's comments about her.

Trump's win in his home state of New York on Tuesday bolstered his chances for the Republican presidential nomination, prompting a more serious study of his prospects in the general election.

Trump will give a foreign policy speech on Wednesday at the National Press Club, part of an expanded policy roll-out the campaign is planning, his aides told Republican leaders and lawmakers this week.

The speech will come the day after a round of primary contests in Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island, in which polls show him likely to do well.

Trump's rivals have said he lacks foreign policy expertise, and several foreign leaders have said they are concerned about the idea of Trump in the White House.

Mexico's new ambassador to the United States, Carlos Sada, vowed on Thursday to combat negative publicity in the U.S. campaign after Trump accused Mexico of sending drug traffickers and rapists into the United States and vowed to build a wall at the border. [nL2N17P00Y]

Japanese firms said in a Reuters poll released on Wednesday that a Trump presidency would harm security partnerships. [nL3N17M2DH]

"Donald Trump speaks in broad themes that resonate with the country, but he also understands that there's a more intricate process in how you run a general election campaign," said Steve Duprey, a Republican National Committee member from New Hampshire who attended a meeting of the group in Florida.

U.S. Republican officials were gathering in Hollywood, Florida to take stock of the race for the White House and prepare for a possible contested convention in July in Cleveland.

Even as Trump aides promised a new emphasis on the general election, his opponents criticized the notion that Trump is assured the nomination.

"The mantra that somehow Donald Trump has become the presumptive nominee after New York is ridiculous," Ted Cruz campaign chairman Chad Sweet said on CNN on Friday.

RNC Chairman Reince Priebus said on Friday that the party was prepared for numerous scenarios, including a contested convention in July if no Republican has earned the 1,237 delegates needed to secure the nomination.

(Reporting by Steve Holland in Hollywood, Florida, and Doina Chiacu and Susan Cornwell in Washington; Additional reporting by Megan Casella; Writing by Emily Stephenson; Editing by Bill Trott, Cynthia Osterman and Mary Milliken)

Editor's note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims -- 1.6 billion members of an entire religion -- from entering the U.S.