Billionaire Republican presidential candidate Donald Trump says he plans to spend at least $2 million (£1.3m) a week on television advertising in the first three voting states.
The move that would mark a massive departure for a candidate who has so far relied on free media to fuel his campaign.
He told reporters invited aboard his private jet that he did not want take anything for granted.
“I don’t think I need to spend anything. And I’m very proud of the fact that I’ve spent the least and achieved the best result,” Mr Trump said before a rally in Council Bluffs, Iowa.
“I feel I should spend. And honestly I don’t want to take any chances.”
He added: “I’ll be spending a minimum of $2 million a week and perhaps substantially more than that.
“If somebody attacks me, I will attack them very much and very hard in terms of ads.”
Mr Trump said he had screened the first two ads and says they touch on immigration, trade and national security policy. When the real estate mogul announced his candidacy in June, he said he planned to spend $35m by Friday. Instead, his reliable tendency for combative language has resulted in a steady stream of media coverage, often stemming from comments made during the five Republican debates or during his speeches at rallies.
Iowa’s caucuses begin the 2016 voting on 1 February, a little more than a month away.
Trump, who leads in national Republican preference polls, has seen his lead dissolve in Iowa, where Texas Senator Ted Cruz is surging on the backing of the state’s robust evangelical conservative voting bloc.