US Democratic presidential candidate Hillary Clinton plans to make job creation the focus of her campaign over the next month, beginning with a $275 billion infrastructure spending plan that will be released this week.

Clinton's plan to increase the federal government's spending on infrastructure by $275 billion over the next five years will be fully paid for by changing how businesses are taxed, a campaign aide said, without providing any details.

Of the total amount, $25 billion will be earmarked for an infrastructure bank. Clinton's campaign estimates her proposals could also encourage private investment that, along with government spending, would inject a total of $500 billion into rebuilding crumbling roads, bridges, buildings and other structures.

"My jobs plan starts with investing in infrastructure," Clinton said on Sunday at the launch of "Hard Hats for Hillary" in Boston, "not just because infrastructure jobs are good-paying jobs, though they are, and not just because we desperately need to invest in building our future again, which we do, but because investing in infrastructure makes our economy more productive and competitive across the board."

The hard hats group is made up of union workers in skilled trades such as carpentry who support Clinton's campaign.

Clinton's campaign cited a recent study that showed the median wages for infrastructure workers, at $38,810 per year, were several thousand dollars higher than the national median for all workers.

Clinton's emphasis on jobs, and infrastructure in particular, is a move to woo working-class voters, who will be critical in the general election in November 2016.

Infrastructure spending is favored by Democrats to spur job growth. US Senator Bernie Sanders of Vermont, who is Clinton's chief rival for their party's nomination, has suggested a $1 trillion infrastructure plan. In President Barack Obama's 2016 budget, he proposed $478 billion for a six-year surface transportation proposal.

In Boston, Clinton noted the construction industry was hit hard during the financial recession and promised to rebuild "ladders of opportunity available to anybody who is willing to work hard" so workers can enter the middle class.

For more on the 2016 US presidential race and to learn about the undecided voters who determine elections, visit the Reuters website. – Reuters