WASHINGTON- U.S. Senator Elizabeth Warren is proposing a new 7 percent tax on corporate profits that exceed $100 million, her presidential campaign said on Thursday.

Warren's proposal would apply the new tax not to the totals companies already report to the IRS, but instead to the profits reported to shareholders - which are frequently much larger given the loopholes, deductions and other accounting differences allowed by the tax code.

Companies would not pay the new tax, which would be in addition to existing corporate taxes that companies already pay, on their first $100 million in profits.

But for each dollar over that threshold, the companies would be subject to a 7 percent tax, Warren outlined in a post on the website Medium and seen by Reuters.

Her campaign estimates about 1,200 companies would be subject to the new tax. It would bring the government an additional $1.05 trillion in new tax revenues over 10 years, according to estimates from economists Emmanuel Saez and Gabriel Zucman at the University of California-Berkeley.

Warren hopes to challenge Republican President Donald Trump, who has focused on tax cuts for corporations, which he says have allowed the economy to flourish and lowered the unemployment rate.

Warren is competing in a crowded field of more than 15 Democrats vying for their party's nomination and has sought to distinguish herself by offering the most numerous and expansive policy proposals.

Warren's new tax, which she dubs the "Real Corporate Profits Tax," would account for profits U.S. companies make globally and would also be imposed on foreign companies doing substantial work in the United States.

"This new tax applies to the profits very large American companies report to their investors -- with no loopholes or exemptions," Warren wrote in her proposal.

Warren specifically targets Amazon.com and Occidental Petroleum as two companies she says are not paying enough in corporate taxes and would be forced to pay more under her proposal.

Republicans are likely to criticize her proposal by arguing that it will drive companies currently incorporated in the United States to leave or change domicile to avoid the tax - a practice known as inversion.

Warren's campaign argues that rules on inversions put in place by the Treasury in 2016 have halted the practice and that she would continue strict enforcement if elected.

(Reporting by Ginger Gibson Editing by Sonya Hepinstall) ((Ginger.Gibson@thomsonreuters.com; 202-898-8482; Reuters Messaging: Follow me on Twitter @GingerGibson))