"I think Donald Trump is terrifying, and I absolutely hate what he stands for," Clinton said in an email to her supporters, hours after Mitt Romney, the 2012 Republican nominee blasted his party's own presidential front runner.

"I hate how he insults women, people of colour, and entire countries when it suits him. I hate his total lack of understanding of complex issues that impact Americans," Clinton, 68, said in her email yesterday.

Earlier in the day, Trump, 69, claimed that he was the only one who can defeat Clinton in the November Presidential elections.

Clinton and Trump fast tracked their race to the White House after posting big wins in the recent crucial multi-state 'Super Tuesday' primaries to stay on course for clinching their parties' presidential nominations.

Both won seven primaries of the Democratic and Republican parties as the possibility of a November presidential election showdown between the two seemed likely.

Clinton has attacked controversial Trump before also.

Attacking Trump's pledge to "make America great again", Clinton said "America never stopped being great!".

Read more: Republican party leadership rally against Donald Trump

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