US Republican presidential frontrunner Donald Trump says he is planning to spend $2m (£1.3m) a week on campaign advertising.

Trump said he would bring out "substantial" adverts in Iowa, New Hampshire and South Carolina ahead of primary elections in February.

Meanwhile, former New York Governor George Pataki has pulled out of the race for the Republican nomination.

Correspondents say he has failed to make any impact in the polls.

Trump, a property tycoon, has previously said that he is funding his campaign himself and wouldn't be in the pocket of lobbyists or powerful corporate entities. He has also insisted that he has spent very little on his campaign so far, and yet is the frontrunner.

"I'll be spending a minimum of $2m a week and perhaps substantially more," Trump said in a video broadcast on CNN.

"I'm going to be doing big ads in Iowa, New Hampshire, South Carolina, and they're going to be very substantial."

Trump's campaign so far has been marked by a series of controversial statements.

Earlier this month, he said Democratic frontrunner Hillary Clinton had been "schlonged" by Barack Obama in 2008, using a vulgar Yiddish term that means a penis.

He said he was referring to s Clinton's defeat to then Senator Obama in the primary contests that year.

He has also called for Muslims to be banned from entering the US following a deadly attack in California carried out by a radicalised Muslim couple.

The billionaire, who has no political experience, leads the polls nationally among Republican voters, and is also ahead in some key states.

In a tweet on Tuesday, Pataki said he was suspending his campaign but was "confident we can elect the right person".

He launched his campaign in May, positioning himself as a moderate in a heavily conservative field.

However, he has barely registered in state or national polls and was not eligible to take part in televised debates involving the high-profile candidates.

Bruce Breton, a member of Pataki's New Hampshire steering committee, said the former governor had told him on Tuesday that he would be leaving the race.

He said Pataki's campaign had struggled to win media attention or to raise funds.

"He said he couldn't get any traction. He worked hard, it's just a different type of year,'' Breton said.

The primary contests begin at the start of February and the presidential election is in November.