WASHINGTON/NEW YORK (REUTERS) - US President Donald Trump's re-election campaign ramped up spending in June as the presidential race intensified, outlaying more than US$50 million (S$69.5 million)- about twice what Trump spent the month before.

Trump ended the month with US$113 million in cash, according to a disclosure filed on Monday (July 20) with the Federal Election Commission.

His rival, former US Vice President Joe Biden's presidential campaign, spent US$36.9 million (S$51.3million) in June, ending the month with US$108.9 million in cash, according to a disclosure also filed on Monday with the Federal Election Commission.

Trump's campaign funnelled money into television ads as public opinion polls showed Biden increasingly building a significant lead ahead of the Nov 3 election.

And while Trump's campaign bought significant television air time across the country, Biden only launched his first major advertising blitz in the second half of June, targeting battleground states like Pennsylvania and Michigan.

The Wesleyan Media Project, which tracks campaign spending, said in a study earlier this month that between May 11 and June 28, the Trump campaign bought 50,000 ads nationwide, while the Biden campaign bought just 3,100 in the same period.

Despite Trump's ad budget advantage, the president has lost ground against Biden in public opinion polls as many Americans have soured on his handling of the coronavirus health crisis.

Biden led Trump among registered voters by 10 percentage points in a Reuters/Ipsos poll conducted July 14-15.