Reacting to former US President Donald Trump's verbal attack, Republican candidate Vivek Ramaswamy said on Sunday (local time) that he is not assigning much weight to Trump's first criticism of his campaign, CNN reported.

Speaking to reporters after a campaign event in Iowa's Ankeny, Ramaswamy said he "doesn't hold it against" Trump that the former US President called his campaign "deceitful."

Speaking to CNN, Ramaswamy said, "I interpret it as bad campaign strategist corporate consultant advice that he might have received, and so I don't hold it against him. ... He's been a great president."

Ramaswamy has said that Trump will not be able to secure victory in the general election due to his strong legal obstacles and political opposition, CNN reported.

Asked whether he believes the timing of Trump's attack suggests the former president may feel threatened by his campaign, Ramaswamy refused to speculate on Trump's intentions, CNN reported. However, he reiterated his belief that his campaign is witnessing a "late surge" in Iowa.

He said, "I can't speak for anybody else's attitude towards our campaign. What I can tell you is that you'd have to have your head stuck in that snow pile to believe that we're not having a late surge here in this race," according to CNN report.

Vivek Ramaswamy's remarks come after Donald Trump launched an attack on party candidate Vivek Ramaswamy, calling his campaign "deceitful" and urging his supporters not to "waste" their vote on him. He said that the Indian-American leader is not 'MAGA' (Make America Great Again) and a vote for him is a vote for the "other side."

In a post on Truth Social, Trump wrote, "Vivek started his campaign as a great supporter, "the best President in generations," etc. Unfortunately, now all he does is disguise his support in the form of deceitful campaign tricks. Very sly, but a vote for Vivek is a vote for the "other side" -- don't get duped by this."

He further stated, "Vote for "TRUMP," don't waste your vote! Vivek is not MAGA. The Biden Indictments against his Political Opponent will never be allowed in this Country, they are already beginning to fall! MAGA!!!"

Notably, this marks a sharp reversal in the way Trump was speaking about Vivek Ramaswamy throughout the campaign. This is the first and most aggressive attack by Donald Trump on Ramaswamy, which comes after a series of comments and posts Ramaswamy made that have angered Trump and his team, according to Trump's advisers.

Previously, Ramaswamy did not criticise Trump. Instead, he often praised him during the campaign trail. On Saturday, Vivek Ramaswamy shared a picture on X that showed him posing with supporters donning "Save Trump, vote Vivek" T-shirts, which showed a picture of Trump's mug shot from when he was processed in Georgia at the Fulton County jail in August.

The post, which was shown to Trump, "infuriated" him, CNN reported citing one advisor. The advisor noted that Donald Trump feels Ramaswamy has been working to undercut his candidacy while falsely painting himself as a Trump supporter.

Trump and his campaign were also annoyed over an interview Ramaswamy gave to NBC News and The Des Moines Register earlier this month. During the interview, Ramaswamy repeatedly described Trump as "wounded."

Ramaswamy said, "They don't have on me what they have on him," stressing that he is better positioned to implement Trump's agenda, CNN reported.

Trump's team insisted they had not seen anything in the polls to indicate Ramaswamy was gaining on Trump in Iowa and this response was based on Ramaswamy's recent comments and posts.

Meanwhile, Republican presidential candidate Vivek Ramaswamy said he believes his campaign is gaining momentum in Iowa one day before the Iowa caucuses.

In the final Des Moines Register poll before Monday's caucus, 8 per cent of caucusgoers said Ramaswamy was their first choice for president, putting him behind Donald Trump, former South Carolina Gov. Nikki Haley and Florida Governor Ron DeSantis.

Speaking to reports in Iowa on Sunday, Ramaswamy said he thinks he will defy expectations on Monday night and said he's looking forward to "delivering a shock to the world," CNN reported.

He was interrupted during his remarks on multiple occasions. Ramaswamy engaged in a series of tense exchanges with a voter who repeatedly interrupted his remarks and he was accosted by the hosts of The Good Liars podcast.

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A voter repeatedly questioned Ramaswamy about his relationship with Trump and whether he would join a ticket with Trump as the vice presidential nominee. In response, Ramaswamy intends to win the nomination and become president.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)