Clinton to release 2015 tax returns within days to pressure Trump: reports
Democratic presidential candidate Hillary Clinton holds a conversation on immigration at Los Angeles Mission College on June 4, 2016 in Sylmar, California (AFP)

U.S. Democratic presidential candidate Hillary Clinton will release her 2015 tax returns as soon as this week in an effort to pressure her Republican rival, Donald Trump, to release his own, CNBC and ABC News reported on Thursday.

CNBC said the returns will show Clinton paid an effective tax rate of 35 percent and gave about 10 percent to charity. Clinton's campaign will also release 10 years of tax returns for her vice presidential running mate, U.S. Senator Tim Kaine, according to the cable network.

Reuters could not immediately confirm the reports, and representatives for the campaign did not immediately reply to an emailed request for comment.

Clinton's campaign has already released tax returns going back to 2007, and has said decades' worth of her tax returns prior to that are publicly available.

Trump, a New York real estate developer, has refused to release his tax returns and said he was unlikely to do so before the Nov. 8 presidential election.

Although U.S. presidential candidates are not required to make their tax returns public, every contender for the White House has done so since 1973.

Critics, including 2012 Republican presidential nominee Mitt Romney, have blasted Trump for failing to disclose his tax rate and raised questions about what his returns say about his net worth as well as his various business ties, particularly in Russia.

Trump and his lawyers have said his returns are under audit by the Internal Revenue Service and that they reveal little.

Asked in a television interview in May what tax rate he pays, Trump replied "It's none of your business."

The IRS has said Trump can release his tax returns even while under audit. Besides showing sources and amounts of income, tax returns show what percentage tax rate a person ultimately pays, as well as how much they claimed in deductions and the amounts given to charities.

Earlier this month, billionaire investor Warren Buffett, a Clinton supporter, challenged Trump to make his tax returns public. Trump declined to do so.

(Writing by Susan Heavey; Editing by Frances Kerry)